London — Prime Minister Theresa May’s Brexit deal wraps "a suicide vest around the British constitution" and hands the detonator to the EU, former foreign minister Boris Johnson said in comments that drew strong criticism.

In an article in the Mail on Sunday newspaper, Johnson pressed his attack on May’s so-called Chequers plan to leave the EU, calling it "a humiliation" that opens "ourselves to perpetual political blackmail".

May is under fire from all sides of the divisive Brexit debate, with Johnson leading a push by eurosceptic legislators for the government to "chuck Chequers" and pursue a clean break with the bloc.

But so far, May has signalled she will not drop her blueprint for Britain’s future ties with the bloc after Brexit.

"We have wrapped a suicide vest around the British constitution and handed the detonator to [EU chief negotiator] Michel Barnier," Johnson wrote.

His words drew condemnation from fellow members of the governing Conservative Party.

Alan Duncan, a minister at the foreign office, said Johnson’s comments marked "one of the most disgusting moments in modern British politics".

"For Boris to say that the PM’s view is like that of a suicide bomber is too much," he said on Twitter. "I’m sorry, but this is the political end of Johnson. If it isn’t now, I will make sure it is later."

Johnson resigned as foreign secretary over the Chequers plan, named after May’s country residence where the government agreed proposals to maintain close trade ties with the EU in July, and has attacked it as making Britain "a vassal state".

Frances O’Grady, general secretary of the Trades Union Congress, said her organisation would back a second vote on Brexit if May failed to win a deal that supported workers.

But two ministers batted away Johnson’s appeal for Britain to drop Chequers and negotiate a Canada-style trade deal instead, saying such an agreement would not solve the problem of a new border between Northern Ireland and EU member Ireland.

"It is not news that he has a difference of opinion with the prime minister and that’s why he left government," interior minister Sajid Javid told the BBC’s The Andrew Marr Show.

Housing minister James Brokenshire urged Conservatives to move forward with the Chequers plan, for which May has failed to win backing from her party, Britain’s parliament and also EU negotiators.

Many of Johnson’s supporters hope his increasingly vocal criticism of May signals that he will launch a leadership bid, while other Conservatives suggest his Mail article was solely to distract attention away from his marital difficulties.

On Friday, Johnson said he had separated from his wife, Marina Wheeler, and that the couple would divorce.