Boris Johnson lashes out at Northern Ireland backstop threat to Union

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.

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.”

While Foreign Office minister Sir 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.”

But in a further indication of the toxic nature of 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.”