Jeremy Hunt, one of the two candidates vying to replace British Prime Minister Theresa May, says rival Boris Johnson is a coward for avoiding public head-to-head debates on what to do about Brexit.
"On the question of debates, he is being a coward," Foreign Secretary Hunt said.
"It is cowardice not to appear in head-to-head debates."
Hunt, 52, said it was disrespectful for Johnson to have turned down the opportunity for a head-to-head debate on Sky television.
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"People need to know what you're going to do and you need to answer those questions," Hunt said. "I promise Boris Johnson the fight of his life and he's going to have that and he's going to lose."
Johnson, 55, is the favourite to win a vote of 160,000 Conservative Party members who will decide who will be the next prime minister. Betting markets give him a 79 per cent implied probability of winning the top job, down from 92 per cent last week.
He has cast himself as the only candidate who can deliver Brexit on October 31 - with or without a deal - while fighting off the electoral threats of Nigel Farage's Brexit Party and socialist Jeremy Corbyn's Labour.
Early on Friday, police were called to Johnson's home after neighbours heard a loud altercation between him and his girlfriend. Police said there was no cause for police action.
The Guardian newspaper, which first reported the story, said an unidentified neighbour had heard Johnson's girlfriend, Carrie Symonds, screaming followed by "slamming and banging".
At one point Symonds could be heard telling Johnson to "get off me" and "get out of my flat". Johnson declined to answer questions about the incident at a hustings event in Birmingham on Saturday.
Hunt said the personal life of Johnson was irrelevant but that the candidates should explain their Brexit positions - and specifically, what would a new leader do if lawmakers tried to sink a new government heading towards a no-deal Brexit.
"If parliament takes no-deal off the table before October 31, will Boris call a general election?" Hunt said. "I think a general election would be catastrophic."
Hunt said he would seek a better deal from the EU to leave on October 31 and would, if absolutely necessary, leave without a deal. If parliament took a no- deal Brexit off the table, he intimated there would have to be delay.
"In that situation, you would have to carry on negotiating," Hunt said. "I want to leave by October 31 but if parliament stops it the prime minister has to obey the law."
Johnson repeated on Monday that he would lead the United Kingdom out of the EU on October 31 with or without a deal.
"We are going to come out of the EU on October 31," he wrote in The Daily Telegraph. "This time we are not going to bottle it."