Prime Minister Theresa May is facing a mutiny in her ranks as Eurosceptic MP Jacob Rees-Mogg pushes for a no confidence motion and four ministers quit.
Leading Brexiteer Jacob Rees-Mogg has submitted a letter of no confidence in Theresa May, as the British prime minister reels from the loss of four ministers - including two from her cabinet - in protest at her Brexit plans.
Brexit Secretary Dominic Raab and Work and Pensions Secretary Esther McVey sensationally walked out of the government the morning after cabinet agreed a draft EU withdrawal agreement in a stormy five-hour meeting.
Two more junior ministers - Suella Braverman at the Brexit Department and Shailesh Vara at Northern Ireland - also quit along with two parliamentary aides.
"You deserve a Brexit secretary who can make the case for the deal you are pursuing with conviction.
"I must resign."
In a letter to Sir Graham Brady, chairman of the backbench 1922 Committee, Mr Rees-Mogg said May's deal "has turned out to be worse than anticipated and fails to meet the promises given to the nation by the Prime Minister, either on her own account or on behalf of us all in the Conservative Party manifesto".
His move is expected to be matched by other members of the European Research Group, which he chairs, hugely increasing the chances of May facing a vote of no confidence in her leadership.
At least 14 Conservative MPs openly said they had submitted such letters, although others could have done so secretly. Forty-eight are needed to trigger a challenge.
Rees-Mogg told journalists the next prime minister should be someone who believed in Brexit.
But a May ally, former interior minister Amber Rudd, told Sky News: "The problem isn't the prime minister. The problem is the challenges she's got to deliver in trying to pull together this Brexit. She's the best person to do it."
The Labour Party said the government was "falling apart".
May's deal came under a hail of criticism in the House of Commons, where only a handful of Tories spoke in favour of an agreement thrashed out in 19 months of intensive negotiations.
There was laughter from opposition benches when the PM said her deal would allow the UK to leave the EU "in a smooth and orderly way" on March 29.
May insisted the deal was in the national interest and offered a future relationship with "a breadth and depth of co-operation beyond anything the EU has agreed with any other country".
May called a news conference at her Downing Street residence to underline her determination to stay the course.
Asked if she would contest any challenge to her position, she replied: "Am I going to see this through? Yes."
Rees-Mogg told May the deal did not match up to her previous promises on quitting the customs union, maintaining the internal integrity of the UK and leaving the jurisdiction of the European Court of Justice.
Raab, 44, was named Brexit secretary in July after the resignation of his predecessor David Davis, who also quit in protest at May's strategy.
At the heart of Raab's criticism was the belief that the pursuit of a temporary customs union with the EU would be the starting point for talks on the future relationship with the bloc, "severely prejudicing" what Britain could achieve.
The shock departures of Raab and McVey came within little more than an hour of one another as May prepared to face MPs.
Their resignations were followed by Anne-Marie Trevelyan quitting as an unpaid parliamentary private secretary in the Department for Education and Ranil Jayawardena leaving the same post in the Ministry of Justice.
'Fed to the lions'
May had secured her cabinet's "collective" approval for the agreement during a stormy five-hour meeting on Wednesday and European leaders hailed the tentative deal.
German Chancellor Angela Merkel said she was "very happy" that the EU and Britain had reached a draft agreement but French Prime Minister Edouard Philippe warned the prospect of Britain crashing out without a deal was "still on the table".
In Brussels, EU President Donald Tusk said member states would have until Tuesday to examine the deal and to agree the wording of a parallel political statement setting out goals for the bloc's future relations with London.
The agreement was also welcomed along the Irish border - the focus of negotiations on a legal guarantee to keep the economically vital frontier between the Republic of Ireland and the British province of Northern Ireland free-flowing.
"If Theresa May has got any sort of a deal I think it's a miracle. She went to the table with very little to offer and asked for a lot," said businessman Patrick Hughes, owner of an animal feed business in the border village of Jonesborough.
"I think she was fed to the lions a bit," he said.