Michael Gove has pushed back against critics saying he should quit the race to be the next Prime Minister over his past cocaine use, saying he was "in it to win it".
At the launch of his Conservative Party leadership campaign, Mr Gove said he was "sure" he would make the final two candidates to be put to a ballot of Tory members, and mocked the frontrunner Boris Johnson, telling him: "Don't pull out".
Asked about the revelation that he had used cocaine while writing newspaper columns that condemned middle-class drug use, the Environment Secretary said: "I explained ... my regret at my past mistakes.
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"But, one of the consequences of having had the chance to reflect on my mistakes, is that when I was Justice Secretary I was determined to ensure that those people who had fallen into the net of the criminal justice system were given all the support, the help and the care they needed in order to achieve redemption and to enjoy a second chance."
He insisted he would not quit the race, saying: "I'm in it to win it. The one thing that I would say is that there are some fantastic people in this room and, more than that, I've been told in the past that I couldn't succeed.
"I was told when I led the Leave campaign 'you're only on 33% in the polls, you guys will tank, you'll lose by a landslide' and we won.
"I was told when I was education secretary 'you'll never be able to transform education in this country, it's eluded every education secretary before you', but we changed it.
"I was told when I arrived at the Department for the Environment 'do you know what, it's an impossible task to please all of these people - you'll either end up upsetting business or losing the trust of green groups' but actually we were able to bring business and green groups together.
"So, every time I've been given a job I've been told it's impossible and have delivered."
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Mr Gove said choosing to put friendships and family ties on the line by leading the Brexit campaign in 2016 was a sign of bravery, and in a veiled attack on Mr Johnson, called on other candidates to get out of their "bunker".
He also said the UK needed a "serious" leader who had been "tested in the heat of battle", adding: “I don’t want a situation where we have Jeremy Corbyn in Downing Street, propped up by Nicola Sturgeon, breaking up our United Kingdom."
Mr Gove said he would be prepared to delay Bexit if talks were progressing. "Yes, I would be willing to delay, for a day, or a week, or whatever is required, in order to get that deal over the line if we were making progress," he said.