2.3 - How legislation becomes law

Bills and their origins

A proposal for a law is different from a government announcement, consultation or promise.

Most important bills are government bills, introduced by ministers to implement policy. Private Members' Bills are introduced by MPs or peers who are not acting as government ministers. They can become law, but limited time and lack of government support often make progress difficult. Both can be public bills, changing the general law. A private bill instead seeks powers for a particular body or individual; “private” here does not mean the same as “Private Member”. Hybrid bills combine public and particular private interests and have additional procedures. The ordinary public-bill route is the focus of this lesson.

Before introduction, a government may consult through a Green Paper, explain proposals in a White Paper or publish a draft bill for pre-legislative scrutiny. These can expose problems before the formal stages begin, but they are not compulsory stages for every bill. A consultation announcement is not proof that Parliament has already passed a law.

Public bills can normally start in either House. Financial legislation subject to Commons financial primacy starts in the Commons. Starting in the Lords does not avoid Commons consideration. In both routes, two chambers usually examine the proposal before they agree a final text. Parliament's general passage guide, checked 2 October 2026, distinguishes bills beginning in each House.

First and second reading

The opening stages separate formally introducing a bill from deciding whether its central principle should proceed.

First reading is the formal introduction. The title is presented, the bill is ordered to be printed and its text becomes available. It is not the main debate on its merits. MPs cannot infer that the Commons supports a proposal merely because it has received a first reading. The first-reading guide describes its formal purpose.

Second reading provides the main debate on the bill's overall principles. The minister or other sponsor explains the proposal; opposition speakers and backbenchers raise arguments and concerns. The House decides whether the bill should move forward. A division at this stage tests acceptance of the principle rather than voting on every detailed provision. If second reading is rejected, the bill does not continue through the usual route.

Suppose an original hypothetical bill creates a national air-quality regulator. At second reading, members debate whether such a regulator is needed, whether it is a proper use of state power, and whether the proposed overall approach is justified. Whether a particular notice must be served within ten or twenty days is normally a detailed amendment issue for later stages. Members may still discuss that detail to illustrate a concern about the principle. The second-reading guide explains the debate's central purpose.

For government bills in the Commons, a programme motion normally sets the timetable for later proceedings. A timetable can organise business and ensure an elected programme is delivered, but tight time limits can reduce examination of contested clauses. Whether a stage exists and whether sufficient time is spent on it are different questions.

Committee examination of detail

Committee stage tests the wording and practical consequences of a bill clause by clause.

A Commons public bill committee is appointed to examine a particular bill in detail. Its membership reflects the party balance in the House; a government with a Commons majority normally has a committee majority too. It can consider amendments, proposals to change the text, and decide whether clauses and schedules should remain. The chair selects and groups amendments for debate. Members of the committee vote; other MPs can propose amendments through committee members. These arrangements permit focused work but can reproduce party discipline.

Public bill committees for bills starting in the Commons can hear oral evidence from experts and interested groups, as well as consider written evidence. A committee dealing with a bill brought from the Lords does not normally take oral evidence. Do not confuse a public bill committee with a departmental select committee: one works on a particular bill; the other investigates a continuing policy or departmental remit. The MPs' procedure guide explains the evidence, amendment and membership arrangements.

Some bills, notably important constitutional measures or parts of financial legislation, are considered by a Committee of the Whole House in the Commons chamber. Every MP can participate. This changes who examines the bill, not the need to scrutinise its details. A programme order can still limit the time available.

In the Lords, committee examination normally takes place in a Committee of the Whole House or a Grand Committee away from the chamber, with all members able to take part. In Grand Committee there are no divisions and changes require agreement; contested amendments can be pursued at a later stage. Lords amendments are not selected in the same way as Commons amendments, and there is normally no guillotine imposing a fixed end to debate. That can allow detailed examination, although it does not ensure every contribution is useful.

Return to the hypothetical air-quality bill. An amendment requiring the regulator to publish reasons for enforcement decisions changes a concrete safeguard. Its value depends on whether it improves accountability without preventing timely enforcement. This is political reasoning about the text, beyond simply saying that a committee “looks at a bill”.

Report and third reading

Report stage lets the wider House revisit the bill after committee work, while third reading concerns the resulting text as a whole.