Boris Johnson, the runaway favourite to become Britain's next prime minister, on Wednesday ruled out working with Brexit figurehead Nigel Farage in trying to secure a divorce deal with the European Union.
"It's a pretty clear no," he said at a campaign event when asked if he would work with the Brexit Party leader.
"When it comes to fighting other parties, dont give them the oxygen of publicity," he added.
Johnson, who campaigned to leave the European Union in 2016, told Conservative Party members that their next leader needed to be "somebody who believes" in Brexit, repeating that he would leave the EU on October 31 without a deal if necessary.
"It is absolutely vital that we prepare for a no-deal Brexit if we are going to get a deal," he told the digital "hustings", a campaign event for party members.
"I don't think that is where we are going to end up - I think it is a million-to-one against - but it is vital that we prepare."
He also said it would be "absolutely crazy" for the next prime minister to call a general election before Brexit was completed, given the current polling results.
"I think that colleagues do see that we are facing, not just the Tory Party but also Labour, we are facing an existential threat," he said.
Johnson is the overwhelming favourite to beat Foreign Secretary Jeremy Hunt in the run-off, to be decided by the party's 160,000 members, but has been hit by questions over his private life after police were called to a domestic 'row' at his house last week.
Hunt, who supported remain in 2016, also warned that the party faces a crisis if it does not deliver Brexit.
"If we have an election before we have left the European Union, it doesn't matter how charismatic a leader you are, we will be thrashed," he said.
The winner of the contest to replace Theresa May as leader of Britain's ruling Conservatives and prime minister will be announced on July 23.
The two candidates were chosen from an original field of 10 by the Conservative party's 313 MPs.