The overwhelming favourite to be the new prime minister vowed to deliver Brexit by the end of October – even if it proved impossible to negotiate a better deal with the EU.
“We will leave the EU on October 31, deal or no deal,” Mr Johnson told an economic conference in Switzerland, adding: “The way to get a good deal is to prepare for a no deal.”
As the frontrunner, the former foreign secretary had been expected to keep a low-profile for a few days, with Ms May not due to carry out her resignation until 7 June.
But he vowed that people would “hear more than you want to hear” about his bid to replace her over the coming days.
Crucially, his public refusal to consider another Article 50 extension at the end of October will pile pressure on the other candidates to do the same.
The greatest fear of Tory moderates is that the demands of the race – to be decided by the Europhobic Tory membership – will push the UK into an even more perilous Brexit stance.
Mr Johnson paid tribute to the outgoing prime minister, saying she had been “patient and stoical” in facing the difficulties created by EU withdrawal.
But he insisted her successor could do things differently, adding: “A new leader will have the opportunity to do things differently and have the momentum of a new administration.”
And he made clear he would see his job, if chosen by Tory members, would be to “get the UK properly out of the EU, to put Brexit to bed”.
The comments came as one bookmaker underlined how it is Mr Johnson’s contest to lose, giving him a 50 per cent chance of winning – way ahead of the second-placed Dominic Raab (14 per cent).
During the speech, the former head of the Vote Leave campaign insisted MPs had to rule out revoking Article 50 after more than 6 million people signed a petition arguing for it as a route to avoid a no-deal Brexit.
He also claimed the UK could forge a “fantastic free trade relationship” with the EU after Brexit, while also becoming a champion for global free trade.
He enjoys the public backing of at least 10 MPs including Jacob Rees-Mogg, the head of the hard Brexit-supporting European Research Group, Zac Goldsmith, the former London mayoral candidate, and John Whittingdale, the former culture secretary.
Many Tory MPs fear a Johnson victory, but there is a growing belief among most of them that it may be impossible to keep him off the ballot.
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