The Brexit party leader urged the clear Tory leadership favourite to call a general election if the Commons blocked a crash-out departure from the EU – arguing he would win a “thumping majority”.
“If he was prepared to do that, of course I'd want to work with them, of course I'd do that,” Mr Farage said.
The comments come after the biggest Conservative donor piled pressure on Mr Johnson, if he wins the race to No 10, “to be willing to work with Farage”.
A snap election would be necessary if he stuck by his pledge to deliver Brexit by 31 October “deal or no deal” – having failed to negotiate a fresh deal and if MPs block a no-deal.
But many Tories fear disaster if they fight the Brexit Party while the UK remains in the EU, after a poll, last weekend, put Mr Farage’s party in first place on 24 per cent, three points ahead of the Conservatives.
Quizzed on a possible pact, at a Daily Telegraph event, Mr Farage called on Mr Johnson to have the “guts” to be defeated at Westminster and then win the public’s backing for leaving without an agreement.
“If he is prepared to be voted down and go to a general election on that ticket then with the support of people like me he would win a massive, thumping majority,” Mr Farage told an audience in London.
“If he was prepared to do that, of course I'd want to work with them, of course I'd do that,” adding: “I'll work with the devil if they're committed to getting us a genuine Brexit.”
Mr Farage described Mr Johnson as an “entertaining” figure with “charisma, humour and humanity. “He's flawed, and I'm very attracted to people like that,” he joked.
Johnny Leavesley, the head of the Midlands Industrial Council – the Conservatives’ biggest donor group – has urged the next prime minister to strike a deal with the ex-Ukip leader.
It could see the Brexit Party agree not to stand against Tory candidates committed to a no-deal, in return for the Conservatives giving Mr Farage’s party a clear run in Labour-held seats.
Mr Johnson was accused of wriggling on his guarantee of a Halloween night exit in last night’s TV debate, but his critics insist he remains committed to it.
None of the contenders were able to explain how the EU could be persuaded to renegotiate the divorce deal to change the terms of the Irish backstop, making a no-deal more likely.
Mr Farage, who quit the Conservatives in 1992, said none of the leadership candidates understood their party would be “finished” if it failed to deliver a clean exit by the current EU deadline.