The European Union has said it is not prepared to renegotiate the deal, but both Hunt and Johnson are promising to do so, and want to take Britain out of the EU by the current deadline of October 31.

The Times reports that Mr Johnson is planning to hold an early general election while Jeremy Corbyn is still around.

Prime Minister Theresa May launched a broadside against populism on Wednesday, using a valedictory speech to encourage her successor to embrace compromise to secure Britain's exit from the European Union.

Asked whether the row would damage the prospects of a UK-US trade deal, Fox, who was in Washington meeting with Ivanka Trump the day before the ambassador resigned, said appetite in both countries to reach a deal was still strong.

Michael Gove today buried the hatchet with Boris Johnson, saying the man he dramatically stopped from becoming Tory leader in 2016 will make "a great prime minister".

Now it is clear the victor must also persuade Brussels to drop one of its most steadfast demands - an insurance policy created to prevent the return of a hard border between EU-member Ireland and British province Northern Ireland.

But EU leaders want to move on from Brexit, and say much will depend on how Johnson - who has cast himself as Britain's Brexiteer-in-chief - acts if he becomes premier.

Lord Newby said Mr Johnson knew he could not win such a vote in the Commons, adding: 'This is the activities of a banana republic, not the mother of parliaments. The EU is determined not to reopen talks on the 600-page-long divorce treaty known as the Withdrawal Agreement.

Britain's next leader will be announced next week, and has to persuade the European Union to restart talks that other European Union leaders have been adamant can not be re-opened, or else lead Britain into the economic uncertainty of an unmanaged exit. "Why would we change anything?"

It is likely that British members of parliament would try to block any no-deal Brexit.

"I've always been willing as a politician to listen to people willing to come up with credible compromises but what I've found so staggering about the Conservative leadership (contest) is it has been played to a tune of growing extremism". The now-invisible frontier between Ireland and the United Kingdom province of Northern Ireland is Britain's only land border with the EU.

Yet doubt remains over Mr Johnson's will or ability to deliver a Brexit in little over three months, while Theresa May's government failed, despite clear and repeated promises, to do so over three years. Parliament traditionally does not sit for around a fortnight leading up to the speech.