Theresa May has issued a last-ditch plea for MPs to back her Brexit deal, after Brussels chiefs issued a letter offering assurances that they do not want the controversial “backstop” to be permanent.

Speaking in a factory in Leave-voting Stoke-on-Trent, the Prime Minister said the letter from European Council president Donald Tusk and European Commission president Jean-Claude Juncker made clear that the backstop was “not a threat or a trap”.

And she said she was committed to working with MPs from across the House to ensure that workers’ rights and environmental standards were protected after Brexit.

Attorney General Geoffrey Cox issued advice that EU assurances on the backstop “would have legal force in international law”, and said the current deal “now represents the only politically practicable and available means of securing our exit from the EU”.

But Mrs May’s hopes that the letter would win over enough MPs to rescue her Withdrawal Agreement looked set to be dashed, as the Democratic Unionist Party – which props up her minority administration – dismissed it as “meaningless”.

“Rather than reassure us, the Tusk and Juncker letter bolsters our concerns,” said DUP deputy leader Nigel Dodds, who called on the PM to demand changes to the Agreement itself.

And Tory MP Gareth Johnson quit as an assistant whip to oppose Mrs May’s plan, saying it was clear there was “no significant change” to the Withdrawal Agreement.

In the Commons, the Prime Minister acknowledged the deal was “not perfect” but urged MPs who had come out against it to give it a “second look”.

“When the history books are written, people will look at the decision of this House tomorrow and ask: did we deliver on the country’s vote to leave the European Union? Did we safeguard our economy, our security and our Union? Or did we let the British people down?” she said.

Labour leader Jeremy Corbyn said she had failed to secure the assurances she had promised and the Government was in “disarray”.

“It’s clear, if the Prime Minister’s deal is rejected tomorrow, it’s time for a general election, it’s time for a new government,” he said.

Earlier in Stoke, Mrs May warned MPs would be behaving with the “height of recklessness” if they rejected her Withdrawal Agreement in Tuesday’s historic vote, when no alternative deal was on offer which was negotiable and respected the 2016 referendum result.

Theresa May
Theresa May toured the Portmeirion pottery factory in Stoke-on-Trent before her crucial speech (Ben Birchall/PA)

The Prime Minister said that the presidents’ letter provided “valuable new clarifications and assurances” to address the concerns of MPs who fear the backstop, which is designed to prevent a hard border in Ireland, could become a permanent arrangement which the UK could leave only with approval from the EU.

She said the letter delivered:

– A commitment from the EU to begin work on a new post-Brexit relationship as soon as the Withdrawal Agreement is ratified

– An explicit commitment that the new relationship does not have to “replicate” the backstop arrangement, under which the UK would remain in a customs union with the EU and be required to observe some of its rules

– Agreement on a fast-track process to bring a new free trade agreement into force, even if some of the 27 remaining members delay ratification

– Acceptance that the UK can unilaterally deliver on commitments made to Northern Ireland, including a “Stormont lock” on new EU laws being added to the backstop

“The letters published today have legal force and must be used to interpret the meaning of the Withdrawal Agreement, including in any future arbitration,” said the Prime Minister.

“They make absolutely clear the backstop is not a threat or a trap.

“I fully understand that the new legal and political assurances which are contained in the letters from Donald Tusk and Jean-Claude Juncker do not go as far as some MPs would like.

“But I am convinced that MPs now have the clearest assurances that this is the best deal possible and that it is worthy of their support.”

In their letter, Mr Tusk and Mr Juncker stressed they were “not in a position” to rewrite or amend the Withdrawal Agreement secured by Mrs May last year.

But they assured the PM that the EU “does not wish to see the backstop enter into force”, as it would represent a “sub-optimal trading arrangement for both sides”.

The EU wants to ensure it would “only be in place for as long as strictly necessary”.

EU Withdrawal Agreement: how MPs could vote
(PA Graphics)

The EU presidents stated: “Were the backstop to enter into force in whole or in part, it is intended to apply only temporarily, unless and until it is superseded by a subsequent agreement.”

With expectations high at Westminster that the Prime Minister is heading for a crushing defeat in Tuesday’s crucial vote, Mrs May issued a plea to MPs concerned about the danger of a no-deal Brexit to back her.

“The only ways to guarantee we do not leave without a deal are: to abandon Brexit, betraying the vote of the British people; or to leave with a deal, and the only deal on the table is the one MPs will vote on tomorrow night,” she said.

“You can take no-deal off the table by voting for that deal. And if no-deal is as bad as you believe it is, it would be the height of recklessness to do anything else.”

But she said that recent events meant a no-deal Brexit was less likely than “a paralysis in Parliament that risks there‪‪ being no Brexit”.

Warning that failure to deliver Brexit would do “catastrophic harm” to trust in the political process, Mrs May said: “We all have a duty to implement the result of the referendum.”

She was speaking as Conservative former ministers Nick Boles, Sir Oliver Letwin and Nicky Morgan put forward a plan to give Parliament control over the Brexit process if Mrs May loses Tuesday’s vote.

Their European Union Withdrawal Number 2 Bill would give the Government three weeks to seek a compromise that can get through the Commons and allow the UK to leave the EU on March 29 as planned.

If that failed, the Liaison Committee – made up of senior backbenchers who chair Commons committees – would be given the job of coming up with its own compromise deal, which the Government would be legally required to implement if approved by MPs.

However, Liaison Committee chairwoman Sarah Wollaston poured cold water on the proposal, saying backbenchers constitutionally “cannot take over conducting a complex international negotiation”.

Former foreign secretary Boris Johnson, meanwhile, criticised “complicated jiggery-pokery” by MPs, warning they were “really playing with fire”.

He told LBC: “I think that people will feel betrayed.

“And I think they will feel that there has been a great conspiracy by the deep state of the UK, the people who really run the country.”

Treasury minister Mel Stride was pictured leaving Downing Street clutching a sheet of paper bearing the words “No food. No Channel tunnel”.

Some in Westminster saw the image as a clumsy attempt to drive home warnings about the danger of a no-deal Brexit. But sources said the note was simply a list of topics he wanted to raise at a meeting, rather than any kind of prediction.

The Treasury declined to comment.

Meanwhile, the chairman of the Commons Northern Ireland Committee, Andrew Murrison, tabled an amendment to the Brexit motion to create a “sunset clause” preventing the backstop extending beyond the end of 2021.