The Prime Minister wrote to MPs warning that if there is insufficient support for her Withdrawal Agreement in the coming days that she could seek an extension to Britain’s EU membership beyond the European Parliament elections.
It came after the DUP - whose support will be crucial if the Government is to win - indicated they would not back her deal, with the party’s deputy leader Nigel Dodds lamenting the PM’s failure to secure any changes to the Northern Ireland backstop while in Brussels.
“Nothing has changed as far as the Withdrawal Agreement is concerned. We will not accept any deal which poses a long-term risk to the constitutional and economic integrity of the United Kingdom,” he said.
Mrs May sought to soften her approach in her letter to parliamentarians, offering to hold talks with MPs and thanking those who have backed her plan previously.
And she laid out the choices available to the Commons after she agreed a delay to Brexit with EU leaders in Brussels on Thursday night.
The PM said the UK could revoke Article 50; leave without a deal; ask for an extension beyond April 12 if her deal is rejected or not voted on; or leave on May 22 if it is finally approved.
Mrs May wrote: “If it appears that there is not sufficient support to bring the deal back next week, or the House rejects it again, we can ask for another extension before 12 April - but that will involve holding European Parliament elections.
“If it appears that there is sufficient support and the Speaker permits it, we can bring the deal back next week and if it is approved we can leave on 22 May.”
It came as ministers moved to try to head off an attempt by MPs to seize control of Commons business in a bid to secure a “softer” Brexit.
A cross-party group of pro-EU MPs claimed they had the numbers to force a series of “indicative votes” on alternatives to Mrs May’s Brexit deal.
But Business Secretary Greg Clark said the Government was prepared to enable Parliament to express a view on the various options if Mrs May’s deal is rejected by the Commons for a third time next week.
Defeat for the Government on Monday on the amendment - tabled by former ministers Sir Oliver Letwin and Dominic Grieve and Labour MP Hilary Benn - would be a further humiliation for Mrs May.
If the amendment is passed, it would pave the way for a series of “indicative votes” in the House on Wednesday, effectively taking control of the Brexit process out of the hands of the Government.
Meanwhile, former environment and Northern Ireland secretary Owen Paterson wrote in the Daily Telegraph that Government must “stand up” for the 17.4 million people who voted for Brexit, adding a March 29 departure “provides the certainty which all sides are craving”.
In reference to the April 12 extension offered by EU leaders, he added: “Apart from the further humiliation of not delivering Brexit on time, what can be achieved in two weeks that has not been achieved in two years?”
Elsewhere it emerged that Tory former foreign secretary Boris Johnson met Mrs May for talks twice this week, including on Friday.
Mr Johnson is said to have asked the PM how she intended to change her approach, and she reportedly set out plans to restructure the Department for Exiting the European Union.
Hundreds of thousands of supporters of a second referendum will march through central London on Saturday, where Labour’s deputy leader Tom Watson is expected to say he will vote for the PM’s deal if it is put to the people.
Meanwhile Labour leader Jeremy Corbyn, who has been reluctant to throw his full weight behind a so-called People’s Vote, will be campaigning in the North West of England.
As Mrs May battles to stay in Number 10, Prisons Minister Rory Stewart said replacing her would not help the situation.
“I would rather she stayed because I don’t believe that changing Theresa May for someone else is going to resolve this problem,” he told BBC Two’s Newsnight.
“The problems are deep in the wounds of the vote, Parliament, the European Union - it’s not about a single individual.”
Education Minister Nadhim Zahawi warned of a “political meltdown” if Brexit is delayed further, and said he was “not prepared” to tell his constituents that the UK would take part in the EU elections.
“If Parliament decides to vote down the Prime Minister’s Withdrawal Agreement then I think it would be political meltdown and Parliament would have failed, he told BBC Radio 4’s Today programme.
“Each and every one of us will have to ask ourselves the question: ‘Am I prepared to go back to my constituents and say we’re not leaving the EU, we’re going to go for a much longer extension, and we’re going to take part in the European elections?’
“I’m not prepared to do that. I don’t think the Prime Minister is prepared to do that.”