Former British foreign minister Boris Johnson has claimed that Prime Minister Theresa May's Brexit strategy has put the UK constitution in a "suicide vest" and handed the detonator to Brussels' chief negotiator Michel Barnier.
His comments provoked an immediate backlash from Tory critics in the latest sign of the bitter Conservative divide over Brexit and the future leadership of the party.
Mr Johnson quit the cabinet in opposition to Mrs May's plan which would see the UK remain closely aligned with EU rules on goods.
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Writing in the Mail On Sunday, he said: "At every stage in the talks so far, Brussels gets what Brussels wants.
"We have agreed to the EU's timetable; we have agreed to hand over £39bn, for nothing in return.
"Under the Chequers proposal we are set to agree to accept their rules - forever - with no say on the making of those rules.
"It is a humiliation. We look like a seven-stone weakling being comically bent out of shape by a 500lb gorilla."
He also hit out at the Northern Ireland "backstop" - the measure aimed at making sure there is no hard border on the island of Ireland.
Under the EU's version of the plan, if no trade deal with the UK resolved the issue, Northern Ireland would effectively remain part of the single market.
Mr Johnson said: "We have opened ourselves to perpetual political blackmail. We have wrapped a suicide vest around the British constitution - and handed the detonator to Michel Barnier.
"We have given him a jemmy with which Brussels can choose - at any time - to crack apart the union between Great Britain and Northern Ireland."
The UK's alternative backstop and the Chequers plan would both mean "agreeing to take EU rules, with no say on those rules", leaving the country a "vassal state".
He said: "We have managed to reduce the great British Brexit to two appalling options: either we must divide the Union, or the whole country must accept EU law forever."
Mr Johnson said there are "far better technical solutions" to the Irish border issue.
His comments drew a furious response from Tory MP and ex-army officer Tom Tugendhat - who has been viewed as a possible rival in a leadership contest.
"A suicide bomber murdered many in the courtyard of my office in Helmand," he said. "Comparing the PM to that isn't funny."
Home Secretary Sajid Javid said: "I think there are much better ways to articulate your differences.
"It's a reminder for all of us in public policy, whichever party we represent, to use measured language because I think that's what the public want to see."
While foreign office minister Alan Duncan said: "For Boris to say that the PM's view is like that of a suicide bomber is too much. This marks one of the most disgusting moments in modern British politics.
"I'm sorry, but this is the political end of Boris Johnson. If it isn't now, I will make sure it is later."
With tomorrow marking just 200 days until the UK's exit from the EU, Mr Johnson's successor as foreign secretary, Jeremy Hunt, pleaded for Tories to get behind Mrs May and the Chequers plan.
Ahead of a potentially difficult Conservative Party conference, Mr Hunt said the Prime Minister's efforts to achieve the best outcome for Britain "will be greatly strengthened if we are united behind her".
