Theresa May faces a leadership crisis after David Davis savaged the Government's approach to Brexit while dramatically quitting as the minister responsible for the UK's departure from the European Union.
His resignation was warmly welcomed by hardline Eurosceptics in the Tory ranks who were already expressing reservations about Mrs May's leadership after her Cabinet agreed a plan which would keep the UK closely tied to Brussels.
The Prime Minister now faces a stormy meeting with Tory MPs and peers in Parliament on Monday evening as she tries to keep her fragile administration together.
Mrs May had hoped that the Cabinet agreement secured on Friday at Chequers would help her deliver the "right Brexit" for the UK, with an offer to Brussels to share a "common rulebook" on goods and form a new UK-EU free trade area.
Mr Davis's departure just 48 hours after being part of the Cabinet that agreed to Mrs May's plans also triggered the resignation of departmental ally Steve Baker, while fellow Brexit minister Suella Braverman is also reported to have stepped down.
In his resignation letter, Mr Davis said the "current trend of policy and tactics" was making it look "less and less likely" that Brexit would deliver on the referendum result and the Tory commitments to leave the EU customs union and single market.
Mr Davis said "the general direction of policy will leave us in at best a weak negotiating position, and possibly an inescapable one". The "common rulebook" plan "hands control of large swathes of our economy to the EU and is certainly not returning control of our laws in any real sense," he wrote to Mrs May. "I am also unpersuaded that our negotiating approach will not just lead to further demands for concessions," he added.
The responsibility for leading the negotiations should now go to an "enthusiastic believer in your approach, and not merely a reluctant conscript", he said. In her reply, Mrs May told him: "I do not agree with your characterisation of the policy we agreed on at Cabinet on Friday."
She said: "I am sorry that you have chosen to leave the Government when we have already made so much progress towards delivering a smooth and successful Brexit and when we are only eight months from the date set in law when the United Kingdom will leave the European Union."