BORIS Johnson brushed off questions about his cocaine use on Friday, saying his experience was limited to a “single inconclusive event”.

Questions over past drug consumption have dominated the leadership contest after Michael Gove was forced to confessed to partaking when he was a much younger man.

However, Johnson has been accused of trying to evade the question.

On Friday he told the BBC that he had only used the Class A substance once.

Johnson described the incident as “a single inconclusive event that took place when I was a teenager and which I have extensively described to the BBC”.

During a 2005 appearance on Have I Got News For You, the Tory said he had been offered a line but had not inhaled.

He said: “I think I was once given cocaine but I sneezed and so it did not go up my nose. In fact, I may have been doing icing sugar.”

It’s not just questions about his use of the Class A drug that Johnson has been accused of evading.

Rivals have criticised him for hiding from the media.

Until Friday, he was the only candidate not to have confirmed willingness to take part in two televised debates, one due to be broadcast on channel four tomorrow, and the other on BBC two on Tuesday.

Jeremy Hunt, who came a distant second in the first round of voting on Thursday, told the BBC: “We can only have that debate if our front-runner in this campaign is a little bit braver in terms of getting out into the media and actually engaging in debates. Engaging in the TV debates.”

The National: Jeremy Hunt

On Friday, in an interview with the BBC’s World At One, Johnson said he would take part in Tuesday’s debate, which will come hours after the second round of voting, meaning that, at most, five contenders will take part.

He said it was “important that we have a sensible grown-up debate”.

“My own observation is that, in the past, when you’ve had loads of candidates, it can be slightly cacophonous, and I think the public have had quite a lot of blue-on-blue action, frankly, over the last three years.”

His campaign team later confirmed he would not be taking part in Sunday’s debate.

In the interview he also said his solution to Brexit was to fix the Irish backstop problems by having border checks further away from the border.

“The obvious way to do it is to make sure that you have checks on everybody who breaks the law, but you do it away from the border,” he said, adding that the full details should be left to work out in the next round of negotiations.

He added: “The facilitations that need to be provided to enable that to take place – those should not be preordained by the backstop.

“They should be remitted into the implementation period for discussion after we have left.”

“Our friends and partners over the channel will say we can’t do this, this is a unicorn,” Johnson said.

“But I think there is a solution to be arrived at in this area, and we should work hard for it.”

Johnson also defended his record as foreign secretary, including his handling of the case of British-Iranian mother Nazanin Zaghari-Ratcliffe, who is imprisoned in Iran for spying.

He wrongly said she had been in the country training journalists, when she had actually been visiting family.

His comment was used as evidence against her in court.

Johnson said: “If you point the finger of blame at me or at anybody who has tried as I did to get Nazanin out then I think you are unintentionally exculpating the people who are really responsible and that is the Iranian Revolution[ary] Guard.”

Asked if he failed to do his homework by not reading his brief, he referred to his time as mayor of London, saying: “Look at the record of what we delivered in London.”

The crowded contest became a little less crowded on Friday when Health Secretary Matt Hancock withdrew his hat from the ring.

Hancock, who was a 100-1 outsider, won the votes of just 20 MPs, including Scottish Tories, David Mundell, Paul Masterton and Andrew Bowie.

He said he’d done better than expected. “I have made the case that I’m the candidate for the future and we need to look beyond Brexit, but it’s increasingly been clear to me that the party, understandably, is looking for somebody to focus on the immediate challenge that we face.”

Hancock said that “it would always have been easier for me to run had Brexit been delivered and that had proved an insurmountable hurdle”.

The remaining candidates need to win 33 votes in Tuesday’s second ballot to progress to the next stage.

The winner of the contest to succeed Theresa May is expected to be announced in the week of July 22.