MICHAEL Gove has taunted Boris Johnson after telling his former Leave campaign partner that if they were the two final candidates in the Conservative leadership race he would have one message for him: “Don’t pull out.”

This was a mocking reference to how the former Foreign Secretary dramatically withdrew from the contest to succeed David Cameron in 2016 after the Environment Secretary declared that Mr Johnson was not fit to be prime minister.

At his campaign launch on the 28th floor of Millbank Tower in central London, the Scot, rocked at the weekend by the revelation he had 20 years ago taken cocaine on several social occasions, brushed aside the charge of hypocrisy made because at the time he was taking drugs, he was critical of other middle class users doing the same.

He again expressed “regret at my past mistakes” but claimed during his time as Justice Secretary he was determined to ensure people who had fallen foul of the criminal justice system had all the support they needed to “achieve redemption and enjoy a second chance”.

On a day of four campaigns – Jeremy Hunt, Dominic Raab and Matt Hancock also launched theirs – the spotlight fell mainly on Mr Gove given the weekend revelations.

The Secretary of State insisted he was a Unionist to “my boot-straps” and said it should be celebrated that so many jobs in Scotland depended on the strength of the Union.

To applause, he said: “It is a remarkable position for the SNP to be in to say: ‘Do you know what, we don’t want extra money or resources for Scotland because we would rather have a narrative of grievance and separatism than improve Scottish people’s lives.’ That is what’s wrong with the SNP.”

But it was Mr Gove’s direct assault on Mr Johnson that was most potent.

He declared: “If I get through – which I’m sure I will – to the final two against Mr Johnson, this is what I will say to him: ‘Mr Johnson, whatever you do, don’t pull out. I know you have before. I know you may not believe in your heart that you can do it. But the Conservative Party membership deserve a choice, so let’s have a proper race.”

The Environment Secretary also took aim at his former Cabinet colleague’s plan to give an income tax cut to middle to high earners in England, insisting the “poor must come first”.

On Brexit, Mr Gove attacked Mr Johnson’s position of “junking” any progress with Brussels on a new agreement if one were not reached in time by the October 31 deadline.

A no-deal, he suggested, would lead to a no-confidence vote in the Tory Government and a general election resulting in Mr Corbyn in Downing St by Christmas, “propped up by Nicola Sturgeon, breaking up our United Kingdom, inflicting Marxist economics on this nation and blighting our children’s future”.

And in what appeared to be yet another dig at Mr Johnson – criticised for his lack of public appearances - Mr Gove added: “We need someone who has been tested in the heat of battle, someone who is prepared to go under the studio arc lights to make the case for Conservatism, someone who will take Jeremy Corbyn at the dispatch box, not hide in their bunker…

“That is why I am now ready to unite, ready to deliver, ready to lead.”

Earlier, Mr Hunt stressed how he was prepared to leave the EU without a deal but signalled he could extend Brexit beyond Hallowe’en if an agreement was in sight.

"Without a deal, any Prime Minister who promised to leave by a certain date would have to call a general election to change the parliamentary arithmetic…If we fight an election before delivering Brexit we will be annihilated,” he declared.

His campaign was boosted by the endorsement of Amber Rudd, the Work and Pensions Secretary, and Penny Mordaunt, the Defence Secretary.

Ten candidates received enough nominations: Mr Johnson; Mr Gove; Mr Hunt, Matt Hancock, Mark Harper, Sajid Javid, Andrea Leadsom, Esther McVey, Dominic Raab and Rory Stewart. One candidate, Sam Gyimah, did not and dropped out. The first hustings before MPs are on Tuesday and the first vote is on Thursday.