Michel Barnier will update ministers from European Union nations on the state of the Brexit negotiations as domestic pressure on Theresa May intensifies.
Boris Johnson claimed Mrs May is on the brink of “total surrender” to the EU over Brexit as he urged the Cabinet to mutiny against the Prime Minister’s withdrawal agenda.
And another Brexiteer former cabinet minister, John Whittingdale, said it was difficult to see how Mrs May’s premiership could continue if MPs rejected any Brexit deal she brought back to Parliament.
Pro-Brexit Commons Leader Andrea Leadsom added to Tory tensions by insisting the UK could not be “trapped” in a backstop agreement without the ability to leave at a time of its choosing.
Former foreign secretary Mr Johnson suggested that if Mrs May’s plans for a backstop customs deal with the EU - aimed at preventing a hard border in Northern Ireland - went through, the UK could be reduced to the status of a colony.
In a stinging attack on the PM’s proposals ahead of a Cabinet meeting on Tuesday, Mr Johnson said Mrs May’s agenda would see the UK “remain in captivity”.
Mr Johnson said plans for a backstop, which would keep the UK in a customs union with the EU if a solution to the Irish border issue could not be found, would be worse than remaining in the EU.
Mrs May is under fire from both wings of the Tory party after the shock resignation from the Government of Mr Johnson’s pro-European brother Jo, who also delivered a withering attack on the PM’s stance.
That move fired speculation that more ministers who backed Remain in the referendum campaign could also quit.
Boris Johnson resigned following the Cabinet session on Brexit at Chequers in July and further details of that crunch meeting revealed Remain-leaning ministers also voiced concerns.
Home Secretary Sajid Javid, Defence Secretary Gavin Williamson and Chancellor Philip Hammond raised concerns about the Chequers plan, the BBC reported.
Mr Javid described the proposal for a common rule book with the EU for goods and agriculture as “very worrying”, while Mr Hammond questioned whether the 27 other countries in the union would accept such a plan, the broadcaster said.
Writing in the Daily Telegraph, Mr Johnson said that even if the Government got the EU to agree to giving London a unilateral exit option from the backstop, it would be meaningless.
“The awful truth is that even if the Cabinet mutinies - as they ought - it will make little difference.
“Even if we agree with the EU that the UK must have a unilateral break clause, so that we can go our own sweet way at a time of our own choosing, it is irrelevant because the programme and ambition of the Government is to remain in captivity, to stay in our cell, even if we are given the theoretical key to escape.”
Former culture secretary Mr Whittingdale said Mrs May would have to go if she could not get a Brexit deal through the Commons.
He told BBC Radio 4’s The Westminster Hour: “I think if the Prime Minister’s Brexit plan doesn’t get through Parliament, I think it’s quite difficult to see how the Prime Minister can continue because she has staked her credibility.”
Remain-supporting former education secretary Justine Greening said she did not think the Chequers plan would get through a “gridlocked” Parliament.
“We should be planning as to how we can put this final say on Brexit in the hands of the British people,” she told BBC Radio 4’s Today.
Hope of getting a deal for the Cabinet to sign off on Tuesday appeared to be rapidly receding, but talks are continuing in Brussels.
The apparent impasse makes it much harder for the PM to secure a special EU conference in November to settle Brexit terms.
But in a sign of Downing Street attempting to push the process forward, Mrs May’s key Brexit adviser Olly Robbins held talks with counterparts in Brussels over the weekend.
Mr Barnier, the EU’s chief Brexit negotiator, will address ministers from the 27 remaining EU nations at a general affairs council meeting in Brussels on Monday.