David Davis has resigned as Brexit Secretary in a major blow to Theresa May.
The Prime Minister is hoping to win over Tory Brexiteers after a backlash against her plans for leaving the European Union.
But the Press Association understands that Mr Davis, who signed up to the plan agreed by the Cabinet at Chequers on Friday, has now quit.
Two senior sources confirmed Mr Davis’ departure from the Cabinet.
His exit may embolden Brexiteer backbenchers with concerns about Mrs May’s leadership.
The move comes on the eve of a major test for the Prime Minister as she faces first the House of Commons and then a potentially stormy meeting of Tory MPs and peers on Monday.
Mrs May is expected to tell MPs that the strategy agreed on at Chequers is the “right Brexit” for Britain.
Mr Davis had come close to resigning before, but Mrs May must have hoped the danger of Cabinet resignations had passed after Friday’s deal at her official country retreat.
Brexiteer Cabinet minister Michael Gove admitted the plan 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.
Foreign Secretary Boris Johnson backed the proposals at Chequers, despite claiming that defending the plans was like “polishing a turd” during the meeting.
But resistance to the plan from hardline Eurosceptics has been growing over the weekend.
Arch-Brexiteer Jacob Rees-Mogg hit out at the “defeatism” in the Government’s plans, warning that he would vote against them – and suggested other Eurosceptics may do the same.
In the Commons, Mrs May will acknowledge that there have been “robust views” around the Cabinet table and a “spirited national debate” since the 2016 referendum decision to leave the EU.
She will say: “Over that time, I have listened to every possible idea and every possible version of Brexit. This is the right Brexit.”
She will tell MPs it was “the Brexit that is in our national interest” and “will deliver on the democratic decision of the British people”.
The Prime Minister will insist the plan, which would see the UK share a “common rulebook” for goods as part of a proposal to create a UK-EU free trade area, still meets her Brexit red lines.
Mr Davis’ decision could now act as a spur to other Brexiteers to take action against Mrs May.
“There’s a lot of unhappiness... is this going to be a proper Brexit?” says Tory euro-sceptic MP Bill Cash on whether Theresa May's position is any more secure since Chequers #Ridge pic.twitter.com/1gNjHRhshx— Trevor Phillips on Sunday (@RidgeOnSunday) July 8, 2018
Letters calling for a leadership contest have reportedly been submitted to the backbench 1922 Committee.
Tory MP Andrew Bridgen told the Press Association: “I can’t support the offer which emerged at Chequers – I think it’s a breach of the red lines, in fact the offer is so poor that I couldn’t support it even if the EU were paying us for it.
“Obviously if the Government and the Prime Minister continue to support that very poor offer then I won’t have any confidence in the Government or the Prime Minister.”
Veteran Tory Eurosceptic Sir Bill Cash told Sky News “there is a lot of unhappiness” with MPs asking: “Is this going to be a proper Brexit?”
He said he had not written a letter calling for a leadership contest, but pointed out “if people were to decide to put in those letters you only need 48”.
David Davis has done the right thing, a principled and brave decision. The PMs proposals for a Brexit in name only are not acceptable.— Peter Bone MP (@PeterBoneUK) July 8, 2018
Peter Bone welcomed Mr Davis’ resignation, saying it was “a principled and brave decision”.
“The PM’s proposals for a Brexit in name only are not acceptable,” he said.
Writing in The Daily Telegraph, Mr Rees-Mogg said: “If the proposals are as they currently appear, I will vote against them and others may well do the same.”
The plan was “the ultimate statement of managing decline” and “focuses on avoiding risk, not on the world of opportunity outside the EU”.
“Pragmatism has come to mean defeatism,” he said.