Davis said the Brexit plan agreed at Chequers leaves the UK in a “weak negotiating position” and that May’s “common rule book” on customs hands Brussels “control over large swathes of our economy”.
In a resignation letter devastating for the PM’s standing with Leavers, he said “the current trend of policy and tactics” made it “less and less likely” she would deliver “on the mandate of the referendum and on our manifesto commitment to leave the customs union and the single market”.
His shock departure was followed by that of Brexit minister Steve Baker as part of a bombshell move on Sunday night.
Passionate Leaver Suella Braverman was also reported to have resigned as Brexit minister, however, she remains in post.
In her reply, May told Davis: “I do not agree with your characterisation of the policy we agreed at Cabinet on Friday.”
But, as a backbench revolt over her Brexit strategy grows, the flurry of resignations signals a clear threat to May’s premiership.
Speculation is mounting that others, including Foreign Secretary Boris Johnson, are ready to quit.
The PM was thought to have secured her Cabinet’s backing to negotiate a softer version of Brexit during a crunch meeting at her country retreat on Friday.
But barely two days after the supposed peace deal between frontline Brexiteers and Remainers was brokered, May has lost three key negotiators.
It is likely to embolden hardline Tory rebel MPs with doubts about May’s leadership. Key Leave influencer Jacob Rees-Mogg, chair of the Eurosceptic European Research Group, hit out at “defeatism” from the Government and confirmed on Sunday that he would vote down any deal based on the Chequers plan.
Conservative MP Andrea Jenkyns, who quit a junior government role earlier this year to “fight for Brexit” and has threatened to vote against May on a Brexit deal, tweeted her approval of Davis’ resignation.
Conservative MP Henry Smith appeared also to support Davis’ stance.
Brexiteer Tory MP Peter Bone supported David Davis’ decision to quit just days after crunch talks at the Prime Minister’s Chequers summit.
“David Davis has done the right thing, a principled and brave decision,” he said.
“The PM’s proposals for a Brexit in name only are not acceptable.”
In her reply to Davis, May was robust about the Chequers agreement. “I do not agree with your characterisation of the policy we agreed at Cabinet on Friday,” she said.
Leader of the Opposition, Jeremy Corbyn, said the Prime Minister “has no authority left and is incapable of delivering Brexit”.
“With her Government in chaos, if she clings on, it’s clear she’s more interested in hanging on for her own sake than serving the people of our country,” the Labour leader said.
Davis’ 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.
May was expected to tell MPs that the strategy agreed on at Chequers is the “right Brexit” for Britain.
Ian Lavery, chair of the Labour Party, said: “This is absolute chaos and Theresa May has no authority left.
“The Prime Minister is in office but not in power. She cannot deliver Brexit and our country is at a complete standstill, while the Tories indulge in their leadership tussling. “We can’t go on like this. Britain needs a functioning Government.”