Primary legislation in Parliament explained

In the 2024-2026 session of Parliament, 389 pieces of primary legislation moved through Parliament as a bill: 61 Government Bills, 320 Private Members’ Bills, and eight Private and Hybrid Bills. Of these, 64 bills made it through all of Parliament’s various stages to reach Royal Assent and eight were Private Members’ Bills (PMBs). 325 of these bills never made it to Royal Assent, sitting at a range of checkpoints in the legislative process. But what do all of these stages mean, and what are the challenges a Bill faces as it moves through each one?

With the King’s Speech and State Opening of Parliament tomorrow, where the government will announce its legislative plans for the parliamentary session ahead, today is the perfect time to dive into the detail of how a Government transforms election rhetoric into the law of the land. 

At the end of a session of Parliament, the point at which Parliament is prorogued, all legislation which hasn’t passed will fall, ending its journey in Parliament by default. Bills which are presented by Ministers (Government Bills) can be subject to a carry-over motion, which allows a bill to remain from one session to the next. Private Members' Bills cannot be subject to a carry-over motion, which is why the Terminally Ill Adults (End of Life) Bill fell as Parliament was prorogued.

PoliMonitor outlines in the pages below how primary legislation, the laws which are created in the United Kingdom by UK Parliament, moves through the formal bill process. It should be noted here that the principle of Parliamentary sovereignty means that primary legislation cannot be the subject of Judicial Review or overturned by the courts. This briefing focuses on primary legislation only, with a focus on bills which originate in the Commons. 

The process of a bill to Parliament 

Bills can start in both the Lords and the Commons. The Government splits its legislative agenda across both houses at the start of a Parliamentary session to avoid either becoming overburdened with legislation. Major government legislation from this session such as the Water (Special Measures) Act, the Data (Use and Access) Act, and the Football Governance Act began their parliamentary journeys in the Lords. Across both houses, the stages are identical, though there are key procedural differences which can have significant legislative impacts. 

Bills can be introduced in Parliament in a number of ways. Most legislation passes through Government Bills driven by the party that controls the House of Commons, but Private Members’ Bills can also be proposed by members of both houses. PoliMonitor will explain how these Bills are tabled in a separate upcoming briefing.

The First Reading 

The First Reading of a bill is the simplest, acting as the formal introduction of a bill to Parliament. A date for its Second Reading in that House is set, a bill number is allocated and an order is made for it to be printed. 

A bill is not debated at this stage unless it is a Ten-minute rule Bill. These are Private Members’ Bills presented by MPs where they give a ten-minute speech in support of their bill. If there is opposition to the proposed bill, one MP is allowed to give a ten minute speech to set out their reasons for disagreement. Though it is rare these bills are opposed, a notable example occurred in October 2025, when Leader of Reform UK Nigel Farage presented his European Convention on Human Rights (Withdrawal) Bill, which would have legislated to leave the ECHR. In a moment of political theatre, Liberal Democrat Leader Sir Ed Davey gave a speech in opposition to the Bill. A division was forced and the Bill was rejected after the Liberal Democrats turned out en masse to vote against it. 

Second Reading

The second stage of the legislative process presents the first opportunity for parliamentarians to formally debate a bill. The bill’s sponsor will then open the debate and make the case for the bill, before a spokesperson for the Opposition will respond. From here, all other MPs will be able to participate. In Private Member Bill debates, the Minister from the Department most relevant to the bill will also respond to the debate at its conclusion. For example, during the presentation of Clive Lewis’s Water Bill, the debate was responded to at its conclusion by the Water Minister, Emma Hardy. For Government Bills, the opening speech is usually made by the relevant Secretary of State, with a different minister responding to the debate at its conclusion. 

Debate in the Second Reading is typically focused on the broad strokes of what a bill aims to achieve; the text of the bill will not be changed and discussions of the bill’s minutiae tend to occur in the following stages. That said, it’s important to follow the discussion at this stage, as MPs will often give indications on the kind of amendments they will look to propose as the bill progresses. In the Crime and Policing Bill Second Reading, Chris Philp indicated the Conservatives’ plans to submit amendments surrounding stop and search; these amendments were indeed tabled. In the same debate, Tonia Antoniazzi set out her aims to decriminalise abortion through the Bill. It’s a reminder that just because changes aren’t being made directly, every stage of a bill’s progress requires analysis. 

At the conclusion of a debate, MPs will vote on whether to take the bill further. Though usually the sitting government’s majority makes passing this stage a formality, the Government’s attempt to pass welfare reforms last summer demonstrated that even this stage can be fraught with danger. 

Dame Meg Hillier’s reasoned amendment threatened to stop the Universal Credit and Personal Independence Payment Bill in its tracks, after more than 100 Labour MPs said they would vote in favour of rejecting the Bill at Second Reading. If the vote fails, the bill falls and its progression ends. 

Opposition resistance at this stage varies: for more ideologically charged bills, the Opposition will rally their MPs to signify their firm stance against the bill. However, where a bill is less controversial in principle, and division is more likely to come from the small print, they might choose to abstain or even vote with the government. 

The Second Reading Challenge

Due to the fact that time for the Second Reading is limited, this is the stage at which legislation is likely to ‘get stuck’ – either because it’s legislation the government doesn’t want passed, or because it simply doesn’t fit into the parliamentary schedule. Of the 320 PMBs tabled in the last session, 278 are listed on Parliament.UK as being at Second Reading.

PMBs which receive a Second Reading must conclude their debate to progress to the next stage. If a bill is still being debated at 2:30pm on a Friday (where PMB Second Readings generally occur), the bill then requires another day for debate to be named, where it will be the last bill on the Order of Business. This means that it is highly unlikely that its debate will continue. If a bill hasn’t been discussed by the end of the day’s proceedings, the question will be put to the House immediately that it receive a Second Reading. If there is unanimous agreement, the bill will be moved to the next stage. However, a Government Whip will typically oppose any bill which the government doesn’t support, meaning a debate will be required at a later date, effectively ending that bill’s chance of passing. 

Committee Stage 

The Committee Stage is where a bill will begin to receive detailed scrutiny. In this stage, a Public Bill Committee is typically formed based on the party balance of the Commons. For Public Bills, the Government sets the amount of time the Committee will last in a Programme Motion. 

Sometimes, a Committee of the Whole House is formed, in which case the entire House of Commons can scrutinise a bill. In this case, the Report Stage which normally follows will be skipped. This tends to only happen for bills of significant constitutional significance, or for a bill which requires urgent passing. Consolidated Fund Bills (Bills which authorise the Government to withdraw money from the Consolidated Fund) do not have a Committee Stage. 

Bill Committee sessions for public bills will be led by Ministers of State from the department rather than the Secretary of State, along with the relevant Shadow Minister. Every clause and its relevant amendments in the bill are debated as in as much detail as the committee members deem necessary. Clauses can be agreed to without division although, most often, a vote will take place if the opposition voice their dissent. 

At the start of the Committee process, especially for major bills, the Committee will host oral evidence sessions with expert witnesses, similar in format to Select Committee hearings. The last of these sessions usually see the Committee posing questions to the Minister on the Committee. 

From here, the Committee moves through each Clause of a bill, discussing whether it should “stand part” (i.e. stay) in the bill. MPs from both the government and opposition parties table Amendments to each clause. MPs introduce amendments and explain their reasoning for why they want them included, before the Minister responds. 

Amendments are tabled through the Public Bill Office and are published the following day, with full “marshalled amendments lists” published for each sitting day of the Committee. The Chair of the Committee, another MP, will work with the Commons clerks to select the amendments, removing those which do not fit the purpose of the bill and grouping them to ensure that debates are not repeated. 

Once all of the clauses in the bill have been discussed, New Clauses are then discussed. Rather than changing individual sections of the bill, these look to add entirely new provisions. How broad these can be depends on the specificity of the bill’s scope. A notable recent example of a New Clause was Tonia Antoniazzi's New Clause 1 to the Crime and Policing Bill, which decriminalised abortion. 

After the discussion, three outcomes can occur. 

• Firstly, an amendment is agreed to unanimously, in which case it is simply added to the bill. However, this unanimous agreement can carry various meanings. Sometimes, it is because the addition is an uncontroversial measure which has cross-party support. Alternatively, it can also mean that the opposition has intentionally chosen not to force a vote on the issue at this point, instead intending to challenge it at a later stage at which they might hope to gain support from government MPs. 

• Secondly, the MP proposing the amendment can choose to withdraw it if it has been rejected by the Government Minister. This doesn’t necessarily mean the government are opposed to the measure - often amendments are withdrawn because the Minister has assured its proponent that the legislation would cover the issue they are concerned about in its current form, or that it will be addressed through future amendments. Some MPs might also be biding their time for the right moment to force a vote on the issue. As ever, the key is to look into the detail of what MPs say in the sessions. 

• Third, a division takes place when there is disagreement on whether an amendment should be added to a bill. Since the Committee reflects the current balance of power in the Commons, divisions in this session have been dominated by the Government, as even one dissenting Labour MP wouldn’t be enough to force an amendment through. If there is a tie in the vote, the Chair will have the deciding vote, with convention dictating that the bill be left unamended. 

In times where no party holds a majority, these Committees could become a major barrier to legislation. Following the 2017 general election, Parliament passed motions which meant that the government would hold a one vote majority on Committees with an odd number of members; in Committees where there was an even number of members, the Committee would be split evenly between Government and opposition MPs. This slender margin in bill Committees, along with the lack of control over the Commons as a whole, has been cited as a major hindrance to Theresa May’s domestic policy objectives. 

As such, amendments at this stage tend to come from the government, rather than their backbenchers or the opposition. That said, it is worth monitoring what opposing parties focus on during these sessions, as these will often constitute the key issues which crop up again as the bill reaches its latter stages. 

Report Stage

The Report Stage effectively opens up the Committee Stage to the whole House of Commons. The changes made by the Committee will be considered, and all MPs can suggest amendments to the bill, which are then voted on. Unlike in the Committee Stage, only Clauses that have amendments proposed to them are debated. 

Amendments are submitted at Report Stage in the same manner as in the Committee Stage. However, it is the Speaker who now chooses amendments and has the deciding vote in the event of a tie. In the Commons, amendments rejected at Committee Stage can be raised again at Report Stage, although precedence is usually given to amendments not already discussed. 

Though not as many changes are made as during the Committee Stage, changes made here can be no less significant. Tonia Antoniazzi’s New Clause to decriminalise abortion was introduced at this stage. Report Stage reflects the first moment where a Government is likely to face a defeat caused by its backbenchers. In December 2023, a New Clause from Dame Diana Johnson forced the Government to pay restitution to victims of the infected blood scandal, causing a Government defeat at the Report Stage after 22 Conservative MPs broke a three-line whip. 

Third Reading

In the Commons, Bills enter Third Reading in the final form it will take before it is goes to the Lords. It has received all of its Amendments and New Clauses, with sometimes whole new chapters added to reflect the scale of change it has undergone. This is particularly evident in the transformation of the Crime and Policing Bill: from when it was tabled to its Third Reading.

The Third Reading tends to involve a much more general debate of a bill, rather than the line-by-line analysis of the previous stages. MPs will often take the opportunity to praise those who they feel have been instrumental in a bill’s success. MPs will then vote for the final time on the bill. The last time a bill was stopped at its Third Reading was in 1977, when the minority administration of James Callaghan was defeated over the Local Authority Works (Scotland) Bill. 

The Third Reading will typically take place very soon after the end of the Report Stage, sometimes even immediately. 

House of Lords 

If a bill is started in the House of Lords, it follows the same stages and processes as if it had originated from the Commons. Once a bill has passed its Third Reading in the Commons, it moves into the House of Lords, and vice versa. Though the stages of the bill in the Lords are the same (First Reading, Second Reading, etc.), there are key differences which affect how a  bill is discussed. For example, it is convention in the Lords that they do not vote a bill down at Second Reading that has already been through the Commons. 

At the Committee Stage, the government is unable to set a time limit on the debate as they can in the Commons, leading to complaints in this last parliamentary session that some major Government Bills have been stalled by endless Lords scrutiny at Committee and Report Stage. 

In the Lords, there are no discussions of whether a Clause should stand part, as in the Commons, meaning that if no amendments are tabled for a Clause, it will not be discussed.

Furthermore, the Committee Stage usually takes place in Committee of the Whole House. Some bills are debated in Grand Committee (which any Peer can join); however, amendments can only be approved with unanimous agreement, unlike in the main chamber where divisions can take place. All amendments at this stage are collected prior to the Committee Stage beginning and must be considered by the Committee. Amendments rejected during Committee Stage cannot be re-tabled at Report Stage. 

At the Lord's Third Reading, amendments for a bill can be tabled, unlike in the Commons. These amendments must be new suggestions, and cannot be ones which have already been debated and voted down. 

The Lords analyse a bill in the same way the Commons do. If a bill is voted through all stages, then it will return to the House of Commons with the amendments the Lords have added to be considered. If a bill is voted down, then it falls, as in the Commons. However, there are several provisions for the government to work around this. 

The Parliament Act 1911 established that, if the government table an identical bill to the one voted down by the Lords in the previous session, then it cannot be blocked again. Furthermore, bills can be labelled as “money bills” if they only concern taxes, loans, or public money, thus preventing the Lords from blocking them. Finally, the Salisbury Convention, which has been in place since the 1940s, dictates that the Lords will not vote down any legislation which constituted part of a government’s election manifesto. 

Consideration of amendments 

Once the Lords have voted in favour of a bill, it returns to the Commons in its amended form, to be considered by MPs. The Commons can then make more changes and return the bill to the Lords (and vice versa) until both Houses agree on the wording of the bill. Amendments can be rejected through an ‘amendment in lieu’, which offers an alternative proposal. If any changes are made, they must then be approved by the other House. This process is sometimes referred to as “Ping Pong”. 

In the unlikely event that the Houses cannot agree on the wording of the bill, it will fall. Although, the Parliament Act of 1911 can once again be used by the Commons to pass it in the following session. In practice, it is quite rare for a bill to fall at this stage, with the Lords often adapting to the demands of the Government. 

This last session of Parliament has seen the Lords butting heads with the Government on a number of occasions, leading to extended sessions of Ping Pong. In June 2025, the Data (Use and Access) Bill was blocked for several days after Baroness Kidron led an effort to strengthen copyright protections for artists against AI companies. As a Parliamentary session reaches its conclusion, the rush to get legislation over the line can mean that votes can take place in the Commons before the Lords vote on them that same day. 

Royal Assent 

The final stage of primary legislation sees a bill receive approval from the Monarch. Today, this process is a formality; the last Monarch to withhold royal assent was Queen Anne in 1708, when she blocked a bill proposing to arm and organise a Scottish militia. Unfortunately for fans of royal grandeur, the King does not sign a bill himself, instead signing a Letters Patent or Commission which declare it has received royal approval. 

After Royal Assent, a bill will become an Act of Parliament, and as such becomes part of UK law. When a bill takes effect will generally be outlined in a commencement clause, which will either provide a date or give powers to the relevant Minister to issue a Statutory Instrument to confirm its commencement. 

Final Considerations

If writing this explainer has demonstrated anything, it is the depth of the UK legislative process. 

Every stage of the process brings potential administrative pitfalls for the government and their opponents; bills can accelerate through the process with ease, while others can become caught in a procedural quagmire which halts progress. It feels cliché to say, but no two bills’ passages through Parliament are the same. 

As with all things in Parliament, the legislative process is steeped in rules, traditions and convention. Understanding this is critical, both for the politicians who walk through the lobbies to deliver their ayes and noes, and for those on the outside who are hoping to drive change.

However, understanding the stages of a bill is only half the challenge. Reading the amendments and listening to comments made by politicians in attendance at each stage is absolutely necessary in order to fully comprehend the progress of any given bill. It is in the detail of the speeches from MPs and Peers where insights around future risks and opportunities can be found.

At PoliMonitor, we monitor and produce in-depth summaries of all legislative sessions, analysing the key themes of what politicians are saying while still providing the key updates on what has been changed in a bill. For more information on this service, please get in touch.