The Conservative party has erupted into open civil war after forceful criticism of Boris Johnson over his description of Theresa May’s Brexit plan as a “suicide vest” prompted counter-accusations of a “project smear” by Downing Street.

The furious exchanges, in which a leading Tory backbencher said she would probably quit the party if Johnson became leader, herald a turbulent run-up to the party’s conference this month, which is likely to be dominated by intertwined rows over Brexit and the successor to Theresa May.

But Johnson further fuelled speculation about his ambitions by using his regular Monday newspaper column to argue that the UK should follow Donald Trump’s example and slash taxes to create a “happy and dynamic economy”.

And the former Brexit minister, Steve Baker, added to the divisions by warning that the Conservative party faces a “catastrophic split” if the prime minister sticks to her Chequers plan for future relations with the EU.

Following days of detailed reports about Johnson’s convoluted personal life after he and his wife of 25 years, Marina Wheeler, announced they were divorcing, the weekend’s news cycle was dominated by his renewed criticism of May’s Chequers plan.

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Writing in the Mail on Sunday, Johnson accused May of repeatedly caving in over Brexit terms to the EU and its chief negotiator, Michel Barnier, saying that “in the talks so far, Brussels gets what Brussels wants”.

He wrote: “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.”

In the most contentious passage, Johnson castigated the so-called backstop plan to ensure no hard Irish border, which would see Northern Ireland effectively remain part of the single market if no other workable solution is found.

Johnson wrote: “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.”

The analogy brought vehement condemnation from a string of senior Conservatives, including two foreign ministers who worked under Johnson before he resigned as foreign secretary in June in protest at the Chequers plan.

Alan Duncan tweeted:

Sir Alan Duncan MP (@AlanDuncanMP) 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. #neverfittogovern https://t.co/rdI0FWQhbi

Alistair Burt said:

Alistair Burt (@AlistairBurtUK) I’m stunned at the nature of this attack. There is no justification for such an outrageous, inappropriate and hurtful analogy. If we don’t stop this extraordinary use of language over Brexit, our country might never heal. Again, I say, enough. https://t.co/DWVuWQgzZy

Tom Tugendhat, the Tory MP and former soldier who chairs the Commons foreign affairs committee, tweeted:

Tom Tugendhat (@TomTugendhat) A suicide bomber murdered many in the courtyard of my office in Helmand. The carnage was disgusting, limbs and flesh hanging from trees and bushes. Brave men who stopped him killing me and others died In horrific pain. Some need to grow up. Comparing the PM to that isn’t funny. https://t.co/IeRWhmhgS9

Another senior backbencher, Sarah Wollaston, said she would most likely leave the party if Johnson took over. “Personally I hope that won’t happen. I don’t think he is fit to lead the country,” she told BBC Radio 4’s The World This Weekend.

Similar pledges have been made in recent weeks by two colleagues opposing a hard Brexit, Dominic Grieve and Heidi Allen. Grieve said Johnson’s phrasing in the Mail on Sunday article was “entirely in character: crude but, for some, entertaining populist polemic.”

He said there was a lack of coherent thought in the article. “He can highlight flaws in the Chequers plan but his alternatives are worse,” he said. “Every option on Brexit is worse than our staying in the EU and he bears a substantial measure of responsibility as to how we got into this mess.”

The scale of the response, alongside reports about the resurfacing of a dossier chronicling Johnson’s personal life, drawn up by May’s aides during the 2016 Tory leadership campaign, brought accusations that No 10 was instigating a campaign to undermine him.

It is understood that several Eurosceptic Tory MPs who back Johnson’s Brexit ideas believe this is the case, and that the seeming aim is to deter the parliamentary party from allowing Johnson to reach the final two of a succession contest, in which he would be the favourite to win a vote of grassroots members.

A Downing Street source vigorously denied this, insisting current staff had never seen the 2016 dossier and played no part in it being leaked.

Andrew Bridgen, the Eurosceptic Tory MP for North West Leicestershire, said: “It’s clear that No 10 have released their attack poodles. It’s unrelenting. It’s Project Smear Boris. Most of the stuff we’ve read in the press in the last 48 hours has been out there for a very long time. You have to ask yourself: why now, and in whose interests would it be? And then you come to a conclusion.”

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The official cabinet-level response to Johnson’s “suicide vest” comment was, by contrast, relatively muted. The home secretary, Sajid Javid, said there were “much better ways to articulate your differences”, telling BBC One’s Andrew Marr Show that politicians should “use measured language”.

The housing secretary, James Brokenshire, told Sky News’s Sophy Ridge on Sunday: “I think he is wrong on this. I think the tone that he has used isn’t right.”

With Johnson and his allies intent on using the party conference to comprehensively derail the Chequers plan, also thus dealing a significant blow to May, the battle lines are set to become further entrenched in the coming weeks.

At the same time he faces renewed questions about his personal conduct, notably reports of multiple affairs, with several reports on Sunday detailing new claims.

Among some moderate Tory MPs, the latest row has brought mainly frustration. “Yes, it’s fair to say we’re getting a bit tired of the Boris show,” one well-connected backbencher said. “It seems to be happening because he can see his window is closing fast. He might well end up getting rid of the PM, but not for a Boris premiership. I don’t think that has occurred to him.”