Westminster is facing another momentous week – one which could decide the fate of Brexit or even lead to a snap general election.

Today: MPs led by Tory Sir Oliver Letwin and Labour's Yvette Cooper will vote tonight on whether to adopt a soft Brexit option, such as a customs union or membership of the single market, possibly accompanied by a second referendum. Last week, MPs rejected all eight Brexit options put to them in a series of 'indicative votes', but supporters of a soft Brexit from both the Tory and Labour benches believe they have a better chance tonight following the third defeat for Theresa May's deal.

Tomorrow: The Cabinet will meet to discuss a response to the votes. If MPs have backed a customs union, Mrs May will have to decide whether to accept a policy opposed by the vast majority of Tory MPs. If she agrees, the issue could tear the party apart. If she refuses, it would result in a constitutional stand-off that could spark an election. Downing Street fears that she could face a Cabinet walkout regardless of what she decides.

MPs led by Oliver Letwin (left) and Labour's Yvette Cooper (right) will vote tonight on whether to adopt a soft Brexit option, such as a customs union or membership of the single market

Wednesday: Sir Oliver Letwin has indicated he will try to seize control of the Commons agenda again to pursue his soft Brexit plan. If Monday's votes were inconclusive, they could be held again, possibly using preferential voting to reduce the options to one. If Monday night's vote produced a solution, but Mrs May refused to adopt it, Parliament could legislate in a bid to force her hand.

Thursday: Allies of the PM have the day pencilled in for a possible fourth attempt to get her deal through the Commons. They believe that, with the majority against her coming down from 230 to 149 then to 58 last week, they have momentum on their side. Ministers are considering an unprecedented parliamentary 'run off' pitting Mrs May's deal against the soft Brexit option chosen by MPs in the hope of focusing the minds of Tory eurosceptics.

Mrs May faces possible resignations from her Cabinet ministers whichever way she goes on Brexit.

Justice Secretary David Gauke said on Sunday that he would quit the Government rather than support a no-deal exit.

Saying the Tories 'did not have the votes' to get the PM's deal through the Commons he said it would not be 'sustainable' to ignore MPs if they back a customs union.

Mrs May has so far strongly rejected the idea of a customs union, saying it went against the Tory manifesto in 2017.

If she does back one she will face a possible Brexiteer walkout from pro-Leave ministers such as Michael Gove or Andrea Leadsom.

Downing Street has made clear that the PM intends to to bring her deal back to the Commons for a fourth vote.

Brexiteers fear that the indicative vote process - controlled by a cross-party group of MPs led by former minister Sir Oliver Letwin - will inevitably lead to a softer Brexit.

Downing Street has made clear that the PM intends to to bring her deal back to the Commons (pictured) for a fourth vote - possibly on Tuesday or Wednesday

No 10 hopes that pressure will lead to more Brexiteers reluctantly backing Mrs May's deal after it cut the majority against it from 230 and 149 in the first two votes to 58 on Friday.

With the Government now up against a new EU deadline of April 12, ministers played down suggestions that Mrs May could call a snap general election to break the deadlock.

Deputy party chairman James Cleverly acknowledged 'sensible and pragmatic' preparations were under way in case Mrs May was forced to go to the country early, but insisted that was not their plan.

'I don't think an election would solve anything. Time is of the essence, we have got Brexit to deliver. We don't want to add any more unnecessary delay,' he told Sky News's Sophy Ridge On Sunday programme.

Mrs May, meanwhile, was said to be '100% focused' on building support for her agreement, with a view to bringing it back for yet another attempt to get it through the Commons.

Former PM Sir John Major warned that a government of national unity could be necessary if Parliament could not agree a way forward.

'I think it would be in the national interest to have a cross-party government so that we can take decisions without the chaos that we're seeing in Parliament at the moment where every possible alternative is rejected,' he told Andrew Marr.