Former London mayor drops bid for No 10 at the eleventh hour, with Theresa May joining justice secretary as frontrunner

Michael Gove sets out his leadership stall on Friday, having ambushed Boris Johnson with a surprise entry into the Conservative leadership battle, a decisive move that killed off the former London mayor’s long-held ambition to succeed David Cameron as prime minister.

The justice secretary stunned Johnson and the rest of Westminster when he announced at 9am on Thursday morning – just three hours before nominations closed for the Conservative party leadership – that he had reluctantly concluded his old friend was not up to the job.

“I respect and admire all the candidates running for the leadership. In particular, I wanted to help build a team behind Boris Johnson so that a politician who argued for leaving the European Union could lead us to a better future,” he said.

“But I have come, reluctantly, to the conclusion that Boris cannot provide the leadership or build the team for the task ahead.”

Gove had been the director of Johnson’s campaign, and the pair had been key allies in the run-up to last week’s referendum, persuading the public to back Brexit. But in the past couple of days, Gove felt that he was unable to support the former London mayor and decided on Wednesday night that he should instead run himself.

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Key Johnson backers, including the pro-Brexit Dominic Raab and small business minister Nick Boles, were summoned to Gove’s Westminster office, and immediately began switching their allegiance to the justice secretary’s campaign.

With his support draining away at extraordinary speed, the old Etonian – who has long coveted David Cameron’s job – went ahead with the press conference that had been planned as the launch for his campaign at a smart Westminster hotel shortly after 11.30 on Thursday morning.

Johnson began in a defiant tone, saying Britain’s next prime minister should take last week’s Brexit vote as an opportunity to “think globally” and “lift our eyes to the horizon”. But the mop-haired politician lost momentum as he spoke, and concluded by saying he would no longer put his name forward to stand as his party’s leader.

“Having consulted colleagues and in view of the circumstances in parliament, I have concluded that person cannot be me,” Johnson told the packed room, stunning MPs who had assembled to show their support, some of whom were tearful.

The Conservative party has been plunged into turmoil since last week’s referendum, which prompted Cameron to announce that he would step down in the autumn, after fighting hard to convince voters to remain in the EU.

Sources close to Johnson later said: “He’s proud to have been one of those who led the campaign for Brexit, and he’s absolutely proud that it has given voice to millions of Britons who have previously felt ignored.

“His role now will be to champion that cause; to ensure that those commitments made by our leaders to the people and the message sent by the people to our leaders is heard.”

They added that he would fight to ensure that politics does not return to “business as usual”.

Gove, who was demoted from the education department by David Cameron after his reforming zeal provoked anger in the teaching profession, is now seen as a frontrunner for the job, alongside Theresa May.

The justice secretary told the BBC in an interview that he believed Britain should be run by someone who believed “heart and soul” that the country should leave the EU. He said he had never wanted to be prime minister, but had decided, “firmly, but reluctantly,” to run. “There were a number of people who had said to me in the course of the week, ‘Michael, it should be you’,” he said.

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Ed Vaizey, one of the MPs who attended a meeting with Gove on Thursday morning, said: “Gove was ready to back Boris; but the closer it got, the harder he thought about it, he thought, it’s not the right person. Follow that through to its conclusion: the logic is, if he doesn’t think Boris can do it, he has to step up to the plate and do it.” He added: “I think he will be a better prime minister than Theresa May.”

The dramatic reversal of fortunes of the two men overshadowed the launch of May’s own bid for the leadership on Thursday morning. The home secretary promised to unify her divided party and underlined her experience running a notoriously tricky department for the past six years.

May stressed that despite having backed the remain campaign, she would not seek to reverse the public’s vote to leave the EU, saying, “Brexit means Brexit”. Asked for her pitch, she said: “I’m Theresa May and I’m the best person to be prime minister.”

She has picked up more than 70 public declarations of support from MPs, far more than any of her rivals. Prominent Brexiter Chris Grayling and health secretary Jeremy Hunt, who had been considering his own run for No10, threw their weight behind her.

Gove was holding a series of one-to-one meetings with parliamentry colleagues to seek to win them over – with a group of some 30 pro-leave MPs who had been intending to support Johnson the most obvious targets.

Backbench MPs will take their choice from a field of five contenders, with work and pensions secretary Stephen Crabb; former defence secretary Liam Fox; and the pro-Brexit energy minister Andrea Leadsom also joining the fray.

Crabb is running on a joint ticket with business secretary Sajid Javid, who would be his chancellor of the exchequer, the pair painting themselves as the champions of working-class voters. He is estimated to have obtained 20 backers.

MPs will vote in a series of rounds, starting next Tuesday, with the weakest candidate knocked out each time, until two names remain to be put forward to grassroots members. A final result will be declared by 9 September.

Some of Johnson’s backers vented their fury at Gove, with many suspecting him of plotting the decision for several days, and announcing it at the last minute in a deliberate bid to scupper the chances of his Oxford Union contemporary. One said: “Anyone can see who has wielded the knife, and how it has been wielded.”

Johnson’s father, who had opposed his son’s stance in the EU referendum, but supported his bid to become prime minister, said the words that sprang to mind as he watched Boris’s speech were, “Et tu, Brute?” supposedly the final words of Julius Caesar and addressed to his friend and killer Brutus.

After Johnson backed out, Tory grandee Michael Heseltine launched a vicious broadside against him, accusing him of leading Britain towards Brexit, but failing to carry out the public’s instructions.

“There will be a profound sense of dismay and frankly contempt,” Lord Heseltine told BBC Radio 5 Live. “He’s ripped the party apart. He’s created the greatest constitutional crisis of modern times. He knocked billions off the value of the nation’s savings.

“He’s like a general who leads his army to the sound of guns and at the sight of the battlefield abandoned the field. I have never seen so contemptible and irresponsible a situation.”

Kwasi Kwarteng, the MP for Spelthorne and a Johnson supporter, said he was switching his backing to May, saying: “This is the kind of thing that you see in student union politics, and we have had enough of it.” He said Gove’s actions were “a spasm of immaturity”.

Facebook Twitter Pinterest Michael Heseltine: ‘Johnson is like a general who leads his army to the sound of guns and at the sight of the battlefield abandoned the field’. Photograph: Andy Hall/The Observer

Another pro-Johnson MP, Nadhim Zahawi, who sat in the front row for his speech, later also said he would back the home secretary, saying: “I have been convinced today by Theresa May that she is the one to deliver. This is a time for experience, and Mrs May has the most of those on offer.”

Johnson had been the triumphant face of the Vote Leave campaign, holding boisterous public events and striking an optimistic note about Britain’s future outside the European Union.

But Conservative insiders suspected him of backing Brexit out of personal ambition – because it would boost his popularity with the Tory grassroots members who will make the final decision.

With financial markets fragile, and many voters uncertain about the consequences of last week’s decision – EU citizens already living in the UK and Britons living on the continents, for example – there had also been growing concern on the backbenches about whether Johnson had the necessary grasp of detail to manage the complex negotiations with the 27 other EU member states that must now take place.