The Brexit endgame now rests on the Withdrawal Agreement Bill (WAB).

The WAB is a fundamentally different exercise from what we have seen so far in terms of the Brexit process. It is a bill rather than a motion, so it can be amended to create legally binding obligations on the government. But  as its  main purpose is to implement the Withdrawal Agreement, an international treaty, it can’t amended in a way that is incompatible with that agreement, if we are to leave with a deal.

As it starts its progress, each stage brings with it a distinct set of strategic choices and opportunities for parliamentarians.

1) Today: Publication and first reading

MPs and experts have argued that the government should have published a version of the WAB much earlier.

Most of the content will be determined by the test of the Withdrawal Agreement – but this will be the first time we see how the government proposes to put it into law.  We will also see whether the government is offering some of the concessions it hinted at on Saturday – for example on Parliament’s future role on the trade negotiations, and on employment and environmental protection.

2) Tuesday: Second reading

The second reading vote on the WAB in the House of Commons, scheduled for Tuesday, is a one-shot game. This could be the first occasion we see if there is a majority for the deal in principle. If the WAB is rejected at second reading it can’t be reintroduced in this parliamentary session.

That basically means the Government would have run out of road, and a general election would be needed to make any further progress.

The strategic choice for MPs at second reading is difficult. If the WAB is rejected then it effectively ends the session straight away.  But MPs could decide to adopt a wait and see approach:  even if the Bill is approved at second reading, it can still be rejected later at third reading. And Parliament can use the passage of the WAB to try to amend it – for example to seek a Customs Union in the future relationship, or make approval subject to a “confirmatory vote”.

Some MPs who dislike the WAB could decide to abstain in the hope that they can amend it at committee and report stage, and then make their final decision at third reading.

3) Tuesday: Commons Programme motion

If MPs approve the second reading, they will then be asked to then approve the programme motion. MPs can make amendments to this motion, which will set out the timetable for MPs’ consideration of the WAB. This is the stage where some bills – for example Nick Clegg’s House of Lords reform bill in 2012 – have died.

The government is likely to propose an extraordinarily condensed timetable to enable it to hit its 31 October exit deadline. The programme motion is likely to propose that all the House of Commons stages are taken this week.

But there will be strong opposition to this. A tight timetable is controversial because of the constitutional significance of the WAB, given the role the Withdrawal Agreement envisages for the European Court of Justice and the amount of delegated powers it is likely to give ministers to enact areas like the Protocol on Northern Ireland. Outside the context of a major national emergency, or a threat to national security, it is highly unusual for a major constitutional bill to be put through the Commons in such a short timeframe.

By way of comparison, the EU (Withdrawal) Bill, which was passed in 2018, had two days of second reading debate, eight days for the committee stage and two days of report stage in the Commons: but these took place over more than three calendar months, allowing time for scrutiny of a highly complex constitutional bill.

The government’s programme motion if passed could lead to a fairly chaotic process. When it comes to negotiating compromises, what normally matters isn’t only the number of days for debate, but the amount of time between the days. Now an extension has been requested, MPs may feel such a curtailed process is unnecessary.

4) Committee stage

As a major constitutional bill, the committee stage will take place on the floor of the House. The committee stage of the process will be dominated by the amendments proposed by MPs.

If the Withdrawal Agreement Bill is amended in a way that risks being interpreted as a failure to honour the commitments in the Withdrawal Agreement, then that will constitute a rejection of the Withdrawal Agreement.

This could be a major stumbling block for those MPs trying to shape or stop the Withdrawal Agreement after second reading. In 1972, when the Commons was considering the European Communities Act, then chairman of ways and means Robert Grant-Ferris made a ruling that amendments which purported to change the text of the treaties were out of order.

On each of these the government will have to weigh the likelihood of defeat and the damage to its objectives.  Time will be very compressed for the normal process of negotiating compromises with backbenchers where it may come under pressure.

In committee stage on the floor of the House, it will be up to the Deputy Speaker Lindsay Hoyle, chairman of ways and means, to decide which amendments get selected for debate, and which of those go to a vote. The main point of contention with the WAB will be whether the bill’s primary aim – to implement the withdrawal agreement – provides justification for not choosing certain amendments.

5) Report stage and third reading

Report stage is when the government will have an opportunity to show its hand and put forward further concessions that respond to amendments proposed by MPs. Report stage would also represent backbench MPs’ last opportunity to amend the bill before it goes to the Lords.

Third reading is then an opportunity for MPs to approve or reject the WAB as amended in committee and report stage. If the WAB has been subject to significant amendments in the Commons, which would seem likely, the third reading could be the critical moment that determines whether the UK leaves on 31 October with a deal.

6) The House of Lords and Ping-Pong

The Government does not have control over the parliamentary timetable in the House of Lords. This makes it difficult to see how it will get the WAB through before exit day, even if an accelerated timetable is accepted by the House of Commons.

The Letwin Amendment and the request for extension means the Parliament does not immediately have to choose between the current deal and no deal at all, giving the space for a longer timetable.

The Lords sees itself as a constitutional guardian, and is almost certain to make amendments on the major areas of constitutional significance.

The Lords’ committees on the constitution and delegated powers will report on the WAB early on. Their recommendations will be highly influential in shaping the amendments proposed.

The WAB is certain to be amended in the Lords. Even if a referendum has been rejected by the Commons, a further referendum amendment could be introduced by the Lords. The Commons will be asked to approve, reject or consider alternative amendments to those proposed made in the Lords. This may go through more than one stage of back and forth between the House of Commons and the House of Lords.

Only when the bill has successfully negotiated all these stages, will the UK will be able formally to  ratify a withdrawal treaty with the European Union.

By Dr Jack Simson-Caird, Senior Research Fellow at the Bingham Centre for the Rule of Law and Dr Alan Wager, Research Associate at The UK in a Changing Europe

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