Conservative Brexiteers have rounded on the compromise deal struck by the Prime Minister with her Cabinet ahead of a crucial meeting on Monday, with several MPs openly raising the prospect of a vote of no confidence in Theresa May.
The proposal to try to keep the UK in a partial customs union, remaining tied to EU regulations on goods and agricultural products and leaving the door open to preferential migration rules for European citizens, drew threats from eurosceptics and calls for Jacob Rees-Mogg to mount a leadership challenge.
Boris Johnson is reported to have attacked the plan as a “turd” during Friday’s 12-hour marathon cabinet meeting at Chequers, but all of Mrs May’s senior ministers backed it and have been warned that collective responsibility will be enforced from now on.
The Prime Minister will update the House of Commons on the new plan today, before addressing a meeting of the 1922 Committee of MPs.
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Downing Street is reported to be braced for a challenge from Brexiteers, which will be triggered if 48 MPs submit letters to the chairman of the 1922 expressing no confidence in her leadership.
"If she sticks with this deal I would have no confidence in it, and if the Prime Minister sticks with this deal I would have no confidence in her," the Tory MP Andrew Bridgen said on Sunday, touting Mr Rees-Mogg as the only successor who could deliver Brexit.
Mr Bridgen said the deal “crosses many of the supposed red lines” set by Mrs May and warned he wouldn’t support it “if the EU were paying us”.
"I'm very, very disappointed with the offer that we've seen coming out of Chequers - I'm disappointed that so-called Brexiteers in the Cabinet didn't pick up the cudgels and fight for a better offer,” Mr Bridgen added.
And the veteran Eurosceptic Sir Bill Cash said: "The question is how do you leave and is this going to be a proper Brexit? There will be a massive discussion about all this."
Mr Cash added: "There are a lot of questions in here, there is a lot of unhappiness, there is a great deal of concern… if people were to decide to put in those letters you only need 48.
“As a matter of fact, nobody can stop them. Once the decision has been taken by those people the chairman of the 1922 Committee has to implement the process."
Former Tory leader Iain Duncan Smith said the Chequers plan appeared to amount to "continued membership" of the customs union and single market, despite the Prime Minister's promise to leave both.
"If the public perceive that not to be delivered then the Government, I'm afraid, will suffer the consequences at the next election," he said.
And an analysis of the Chequers statement passed between Brexiteer Tory backbenchers claimed the compromise would "lead directly to a worst-of-all-worlds 'black hole' Brexit where the UK is stuck permanently as a vassal state in the EU's legal and regulatory tarpit".
The damning briefing by Martin Howe QC was not endorsed by the European Research Group of MPs, but was circulated by its members at the weekend.
Environment Secretary Michael Gove admitted the plan, which will see the UK tied to EU rules on goods, was not everything he had hoped for but he was a "realist" and the Prime Minister's lack of a Commons majority meant the "parliamentary arithmetic" was a factor in deciding what could be adopted.
Mr Gove said the Prime Minister "allowed us, during the course of a day [at Chequers], to share views, to share analyses and to look at this proposal in detail but at the end of it collective responsibility reigns".
Asked if Mrs May’s compromise was everything he hoped for as a former co-chairman of the Vote Leave campaign, Mr Gove told the BBC's Andrew Marr Show: "No, but then I'm a realist and one of the things about politics is you mustn't, you shouldn't make the perfect the enemy of the good. One of the things about this compromise is that it unites the Cabinet."
He added: "All those of us who believe that we want to execute a proper Brexit, and one that is the best deal for Britain, have an opportunity now to get behind the Prime Minister in order to negotiate that deal."
But Mr Gove warned that unless the EU showed flexibility and accepted the latest proposal, despite suggestions that it will divide the ‘four freedoms’ at the heart of the European single market, "we will be in a position in March 2019, if we don't get the deal we want, to be able to walk away”.
With the Chequers agreement summarised in a three-page note, the full detail of the government’s proposals won’t be known until Thursday, when a detailed White Paper on the UK future relationship with the EU will be published.
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The EU is expected to respond negatively to the plans despite the Irish Foreign Minister saying the plan “deserves detailed consideration”.
In interviews yesterday, Mrs May called on Brussels to “get serious about this, to come round the table and discuss it with us,” and insisted: “I won't let people down".
The Prime Minister told the BBC: "We're leaving the European Union. I think when people voted to leave the European Union, they wanted an end to free movement - free movement will end.
"They wanted us to end the jurisdiction of the European Court of Justice in the UK - that will end.
"They wanted us to stop sending the vast sums of money every year to the EU that we do today, and so take control of our money, our laws and our borders - and that's exactly what we will do.
"But we'll do it in a way that protects drops and enhances our economy for the future."