Boris Johnson has rejected an electoral pact with Nigel Farage, warning that voting for the Brexit Party risks handing Number 10 to Jeremy Corbyn.

The Prime Minister last night dismissed a call by Mr Farage jointly to secure a “big majority” for Leave in House of Commons by standing aside in 150 seats that would “never” vote Conservative for “cultural reasons”.

Mr Farage threatened to field candidates in every constituency bar Northern Ireland if the Tories refuse, a "kamikaze" strategy derided by insiders as an attempt to reconcile differences between a faction which hates Mr Johnson's deal and another which believes the Brexit Party has served its purpose.

The ultimatum also provoked a withering backlash from senior Eurosceptic Conservatives, who accused the Brexit Party leader of putting his “ego” and his party’s prospects ahead of the national interest.

Asked if he would consider any sort of pact, Mr Johnson told the BBC: “Voting for any other party simply risks putting Jeremy Corbyn into Number 10.

“And the problem with that is that his plan for Brexit is basically yet more dither and delay.”

At a launch event in London, Mr Farage promised to fight the Conservatives across mainland Britain unless Mr Johnson scraps his withdrawal agreement and promises to secure a Canada-style free trade agreement by July, or leave on World Trade Organisation terms.