Mrs May was defiant in an afternoon press conference, warning that if politicians reject her Brexit deal, it will set the country on “a path of deep and grave uncertainty.”

Two Cabinet ministers have resigned in the 24 hours since her government backed the deal announced on Tuesday. An increasing number of government MPs are calling for a no-confidence vote on the prime minister, but she told reporters she would resist a leadership challenge, saying: “Am I going to see this through? Yes.”

Mrs May managed to get Cabinet support for the controversial Brexit plan at a five-hour meeting on Wednesday evening (local time). She now must win approval from a divided House of Commons, where she has no majority — but there is a chance she may not survive that long.

Her former foreign minister, ex-London Mayor Boris Johnson, joined an emergency meeting of MPs on Thursday afternoon local time, where plotters were set to launch a formal challenge to the PM after a wave of resignations over the deal.

Mr Johnson quit his post in July because he was unhappy with Mrs May’s handling of Brexit negotiations.

MPs from her Conservative Party need 48 letters of no confidence to be sent to trigger a leadership election — it is estimated there were over 40 this morning and Sky News had been told the 48 had been reached.

Prominent Brexiteer Jacob Rees-Mogg was among the MPs calling for a no-confidence vote.

Mrs May earlier defended her plan in parliament, saying: “British people want us to get this done”.

The developments come after the man charged with leading the Brexit strategy, Brexit Secretary Dominic Raab, sensationally quit, soon after the Northern Ireland Secretary Shailesh Vara announced he was leaving.

Within minutes another frontbencher, Esther McVey, the Work and Pensions Secretary also left the government.

Mr Vara quit first thing Thursday morning London time saying he could not support the withdrawal agreement.

A junior Brexit minister also quit, as did two parliamentary private secretaries.

Pro-Brexit politicians say the agreement, which calls for close trade ties between the U.K. and the bloc, would leave Britain a vassal state, bound to EU rules that it has no say in making.

The deal included features to reduce disruption to business and ensure a seamless — and without checks or need for border control — in Ireland, but that would require the UK to follow EU customs and single market rules that it will have no power over — a hybrid of the current Customs Union and Single Market which Mrs May had vowed to leave.

Mrs May hailed the agreement though as in the “national interest” and warned it was either “my deal. no deal. or no Brexit.”

“When you strip away the detail, the choice before us is clear. This deal, which delivers on the vote of the referendum, which brings back control of our money, laws and borders, ends free movement, protects jobs, security and our Union — or leave with no deal or no Brexit at all.”

In his resignation statement, published on his Twitter account, Mr Raab said the deal failed to leave the UK as a “sovereign, independent country”.

The agreement “leaves the UK in a halfway house with no time limit on when we will finally be a sovereign nation”, he wrote.

The plan has been slammed by Britain’s national papers, with the top-selling Sun splashing with ‘We’re in the Brexsh*it’ this morning.

The 585-page agreement was published with a shorter political statement on ambitions for a future relationship. EU leaders will now get their say, before a vote in the House of Commons.

Ms May still faces an uphill task getting her deal through the divided House of Commons, where her Conservative Party doesn’t have a majority and rebel MPs are expected to cross the floor to vote against the deal.

Ms McVey blasted the agreement, saying it “does not honour the result of the referendum” and could break up the UK.

NO CONFIDENCE

Mrs May only has a majority in parliament thanks to the votes she receives from Northern Ireland’s Democratic Unionist Party (DUP). But they all but confirmed they would not continue supporting her government because their view is the deal breaks up the UK.

DUP deputy leader Nigel Dodds told the Prime Minister this morning: “We stand up for the whole of the UK, the integrity of the UK or we vote for a vassal state with the break up of the UK.”

Mr Dodds said the threat of breaking up the union was clearly an important factor in their decision, but listing the PM’s promises on Northern Ireland back to her would b a “waste of time”.

“Clearly she doesn’t listen,” he added, saying Britain would in future be subject to the “rules and laws of others”.

News of the deal sparked a furious response in the UK.

Nigel Farage, who headed the pro-Brexit campaign, savaged the agreement as the “worst deal in history”.

“Any cabinet member who is a genuine Brexiteer must now resign or never be trusted again, this is the worst deal in history,” he said.

Commentators have noticed a key line used by Ms May in a doorstep interview after the vote.

She referenced a choice between “this deal, no deal and no Brexit”.

Labour MP for Tottenham David Lammy said Ms May had made a “huge concession”, adding that this meant, “Brexit is not inevitable.

“We do not have to choose between her atrocious deal and no deal at all. We can still remain in the EU.”

More to come

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— with The Sun and agencies