Boris Johnson has faced a Tory backlash over his claim that Theresa May’s Brexit strategy had put the UK in a “suicide vest” and handed the detonator to Brussels.
One senior minister said the comments marked the “political end” of the former foreign secretary, while Cabinet ministers criticised his incendiary language.
Mr Johnson launched the attack amid further focus on his private life following the announcement that he has separated from his wife Marina Wheeler and the couple are divorcing.
The prominent Brexiteer’s latest assault on Mrs May’s handling of negotiations with Brussels fuelled speculation about his own leadership ambitions.
Mr Johnson quit the Cabinet in opposition to Mrs May’s Chequers plan which would see the UK remain closely aligned with EU rules on goods.
Writing in the Mail On Sunday, he said: “It is a humiliation. We look like a seven-stone weakling being comically bent out of shape by a 500lb gorilla.”
He also lashed out at the Northern Ireland “backstop” - the measure aimed at making sure there is no hard border with 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.”
Home Secretary Sajid Javid rebuked his former Cabinet colleague, saying: “I think there are much better ways to articulate your differences.”
He told the BBC’s Andrew Marr Show that politicians should use “measured language”.
Communities Secretary James Brokenshire told Sky News’ Sophy Ridge On Sunday he thought Mr Johnson had used the wrong “tone” in the article.
The former Cabinet minister’s 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.”
Government minister Sir Alan Duncan, Mr Johnson’s former deputy at the Foreign Office, 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.”
But in a further indication of the toxic relations within the Tory party, Brexit-backer Zac Goldsmith responded to Sir Alan by saying: “There are a number of possible motives behind this tweet, but given its author, we can be certain ‘principles’ aren’t one of them.”
Mr Johnson’s own leadership ambitions may have suffered a blow by the revelation that his marriage has broken down, although some Westminster commentators suggest having the break-up made public now clears away a potential obstacle on the way to Number 10.
In a sign of the febrile atmosphere within the Conservative Party, the Sunday Times reported that Mrs May’s aides had drawn up a dossier on Mr Johnson at the time of the 2016 leadership contest.
It was not used after his campaign failed to get off the launch pad, but the newspaper reported the 4,000-word “war book” was circulating in Westminster last week amid claims “black ops” attacks were being planned against the prominent critic of the Chequers plan.
Officials at Downing Street and Conservative Campaign Headquarters (CCHQ) denied circulating the document.
Brexit-backing Tory Ross Thomson questioned what Number 10 was playing at and said he was “very disappointed” with the “gutter politics”.
With Monday 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”.
In a Mail On Sunday article, he said: “We should not rush to judgment on a deal that is still under negotiation.
“Nor should we assume that unacceptable further concessions will ‘inevitably’ be made on the Chequers proposals. I know this Prime Minister and she would never recommend a deal inconsistent with what the country voted for.”
In a pointed remark apparently aimed at Brexiteers, he added: “Nobody else has a detailed plan that both delivers on the instruction of the British people and has a chance of succeeding in the negotiations.”
Mr Javid acknowledged the Canada-style trade deal sought by Brexiteers had “a lot to commend it” but would not resolve the Irish border issue.
“The only deal that we have got on the table - that’s the Chequers deal,” he said. “It’s up to the EU to respond to that.”