This week sees some important votes in the House of Commons, which could determine the shape of Brexit and the fate of our Prime Minister. On Tuesday and Wednesday MPs will vote on a series of amendments to the EU Withdrawal Bill, with a number of amendments made by the House of Lords plus some further proposals from MPs and from the government. Three of these votes will be most critical:

- a requirement for Parliament to have a ‘meaningful vote’ on whatever deal is agreed between the UK and EU later this year. Crucially this amendment provides for Parliament to direct the government’s negotiations in the event of failure to agree a deal or rejection of the deal by Parliament.

- a requirement for ministers to report to Parliament by October on steps taken to continue to participate in a customs union with the EU. This is tantamount to instructing the government to make membership of a customs union an objective for Brexit negotiations with the EU.

- a requirement on the UK Government to seek membership of the European Economic Area (the Norway model – in essence continued membership of the single market). The Labour party leadership is calling on its MPs to abstain on this Lords amendment and to vote instead in favour of their own amendment, which would commit the Government to seek “full access to the internal market of the European Union ... with no new impediments” – a slightly more ambiguous version of EEA membership.

Looking at what may happen this week, there are three possible scenarios:

1. One or more of these amendments is passed and the government is defeated. Any of these three amendments would be seen as Parliament taking charge of Brexit negotiations; and the latter two would fundamentally change the government’s Brexit negotiating position. In this scenario, it is possible that the Prime Minister would resign. It is also possible that this outcome could prompt Conservative MPs to challenge Theresa May’s leadership and seek a more ‘hardline’ Brexiteer Prime Minister. There is an outside possibility that the Prime Minister could call an election – on the basis of putting these issues to the country. Alternatively, the Prime Minister may accept the will of Parliament and amend her government’s negotiating strategy accordingly. Any of these is possible. Such is politics at the moment.

2.  It is also possible that the Lords and Labour amendments are all defeated by a majority of ten or more votes. This would be seen as a strong victory and endorsement of the government’s approach. That still leaves the cabinet to agree the precise details of their approach: for example on ‘Max Fac’ versus ‘Customs Partnership’ and the so-far-avoided question of how to ensure regulatory convergence between Northern Ireland and the EU as part of a ‘back stop’ to avoid a hard border in Northern Ireland (last week’s customs proposalonly covers half the problem).

3. The most likely outcome is that these critical amendments will be defeated by a very slim majority with some Conservative back bench rebels or abstentions. And at the same time, Labour MPs will defy their party leadership and vote in favour of the Lords EEA amendment. The amendments will be rejected, the government can proceed, but both party leaders will have had a shot fired across their bows by their backbenchers and will be vulnerable to further possible rebellions. Further opportunities for Parliament to exert itself in cross-party rebellion will occur again when the Brexit Customs Bill returns to the House of Commons in the coming weeks and in the autumn when there will be further debate on the negotiations.

We can certainly expect continued debate about customs: whether a Customs Union, Customs Partnership or Max Fac. As always, there are things that business can do to prepare regardless of the political uncertainty and my colleague Louise Scholey and our customs experts have produced a simple guide to navigating the customs debate.

Whatever the outcome of parliamentary business this week, we are unlikely to see any immediate clarity. We may even see further volatility and uncertainty. As ever, ‘plan for the worst, and hope for the best.’ By assessing the risks of different outcomes you can identify ‘no regrets’ planning decisions as well as being clear about what you would need to do when under different scenarios.