THERESA May is set to put just part of her Brexit deal to the Commons today, in a last ditch attempt to get it past MPs.

It was confirmed late yesterday afternoon that Parliament would vote on the Withdrawal Agreement.

The document sets out the terms of the divorce.

Unlike in the two previous Meaningful Votes, MPs will not have their say on the Political Declaration, which sets out a rough sketch for the future relationship between the UK and the EU. But the Prime Minister faces almost certain defeat, with the DUP, who prop up the minority Tory Government, making it clear that they cannot stomach the Withdrawal Agreement as long as it contains the backstop, the safety net, that prevents a hard border on the island of Ireland.

It’s not just the Northern Irish Unionists who look set to reject May’s deal, Labour, the SNP, the LibDems and at least 30 of her backbenchers will all likely say no too.

There’s also some debate in over the legality of what the Government is doing.

Nicola Sturgeon tweeted: “Part of the problem already with the Withdrawal Agreement and Political Declaration is that it means agreeing to leave the EU with no clarity about the future ie a blindfold Brexit. Take away the Political Declaration completely and that problem is compounded.

“Why would MPs agree to that?”

Labour shadow Brexit secretary Keir Starmer said the EU had made it clear that the two documents, “while being of a different nature, are part of the same negotiated package.”

He added: “Following the PM’s commitment yesterday to resign before the next phase of negotiations begin, if the Withdrawal Agreement passes without a credible plan for what happens next then Brexit is going to be determined by the outcome of the next Tory leadership contest.”

Earlier this month, the EU said the UK could delay Brexit until 22 May if the withdrawal agreement got through Parliament.

But if it doesn’t, then the UK only has until April 12 to find a solution – which would almost certainly mean a hard Brexit or a very lengthy extension.

Number 10 hoped to win over some of the wavering Brexiteers in the Tories by effectively making today’s vote a straight a choice between May’s Brexit deal and a short delay, or that a long delay, and the need to stand candidates in upcoming elections to the European Parliament.

Leader of the House of Commons Andrea Leadsom said the motion gives “Parliament the opportunity to secure that extension.

She added: “I think we can all agree that we don’t want to be in the situation of asking for another extension and facing the potential requirement of participating in European Parliament elections.”

There is some symbolism in MPs being in the Commons on March 29, the day the UK was supposed to leave Europe.

It could be difficult for MPs representing leave backing constituencies to vote to postpone Brexit.

Adding pressure to the Brexiteers will be the thousands of protesters expected outside Westminster, with Ukip and Tommy Robinson – who is behind the racist English Defence League – hosting a Make Brexit Happen rally in Parliament Square.

Downing Street also hope that some opposition MPs might be willing to back the deal, if it’s uncoupled from the declaration. May’s de facto deputy, David Lidington, told the British Chambers of Commerce conference in London yesterday: “If you believe in delivering the referendum result by leaving the EU with a deal then it is necessary to back the Withdrawal Agreement.

“Whether a particular MP wants the final destination to look like Norway or look like Canada or look like the proposals in the Chequers white paper, the starting point is the Withdrawal Agreement itself.”

If the Government wins tomorrow it could then retrospectively amend section 13 of the EU Withdrawal Act, which requires MPs to pass both a resolution combining the Withdrawal Agreement and the Political Declaration.

There have been questions over the legality of this.

Geoffrey Cox, the attorney general, has insisted that this is legal, and has said he will set out the legal case when he opens the debate today.