Boris Johnson promised the “guts and the courage” to take Britain out of the EU by October 31 as he launched his campaign to become prime minister.
The former foreign secretary said the time had come “to remember our duty to the people and the reasons for the Brexit vote”.
He promised to provide the “clarity” of vision needed to deliver the result of the EU referendum with or without a deal, and warned MPs they would face “mortal retribution” from voters if they tried to stop Brexit.
Mr Johnson relied heavily on his record during eight years as Mayor of London as evidence that he could beat Labour at the ballot box, and after facing questions about his integrity he insisted: “I do what I promise to do as a politician.”
Hours later his plans were given a huge boost when an attempt by Labour and Remain-supporting MPs to block no deal flopped in the Commons. Eurosceptics were jubilant after the effort to hijack the parliamentary timetable in order to pass legislation preventing a no deal Brexit was defeated by 309 votes to 298.
The result silenced critics of Mr Johnson, including the Chancellor, Philip Hammond, who had earlier accused the leadership front-runner of promising the “impossible” with his pledge that there would be no further Brexit delays.
Mr Johnson moved a significant step closer to Downing Street on Wednesday as he secured the backing of 81 MPs, more than twice as many declared supporters as any other candidate.
As Tory MPs hold the first round of voting in the leadership election on Thursday, Mr Johnson knows he will effectively be through to the final head-to-head if he can secure 105 votes, which would be more than a third of the parliamentary party.
MPs are already debating whether other candidates will now pull out rather than facing a lengthy battle with Mr Johnson if he has the backing of both Tory MPs and members.
Speaking in front of a broad coalition of supporters from both the Leave and Remain wings of the Conservative Party, Mr Johnson said he would “unite this country and unite this society” by completing Brexit.
He said he was not “aiming” for a no-deal Brexit but it was “astonishing that anyone could suggest dispensing with that vital tool of negotiation”.
Better and “vigorous” preparation for no deal is needed, he said, because: “It is only if we have the guts and the courage to get ready for it that we will carry any conviction in Brussels and get the deal we need.”
Asked about those who want to stand in the way of Brexit, he said: “I think maturity and a sense of duty will prevail. I think it will be very difficult for friends in Parliament to obstruct the will of the people and simply to block Brexit.
“I think if we now block it, collectively as parliamentarians we will reap the whirlwind and we will face mortal retribution from the electorate.”
Mr Johnson also said the British people wanted a “resolution” to Brexit, adding: “That is our mission today and that is why I am standing before you because now is the time to remember our duty to the people and the reasons for the Brexit vote.”
He said the Tory leadership contest was merely “the opening salvo in a battle to restore faith in our democracy...and to protect this country from the red-toothed, red-clawed socialism of today’s Labour Party”.
Geoffrey Cox, the Attorney General, on Wednesday became the 81st MP and the sixth Cabinet minister to come out in support of Mr Johnson.
If Mr Johnson can secure 105 backers, meaning he would have more than a third of Tory MPs behind him, he would effectively be through to the final head-to-head because it is mathematically impossible to have three candidates with more than a third of the vote.
Michael Gove, Mr Johnson’s arch-rival, currently has 32 public backers, two ahead of Jeremy Hunt, while Dominic Raab has 22 supporters, Sajid Javid 18 and Matt Hancock 16.
If MPs currently backing other Brexiteer candidates such as Mr Raab, Esther McVey and Andrea Leadsom switch their votes to Mr Johnson as back markers are eliminated, Mr Johnson would have 121 votes, more than enough to reach the last two.
Tory MPs will hold the first leadership vote on Thursday, with the result being announced at 1pm. The last-placed candidate will be eliminated, along with any candidate who fails to get at least 16 votes.
Four further votes are planned for next week, but with Mr Johnson building such a commanding lead few MPs believe all four elimination rounds will be needed.
One prominent supporter of Mr Johnson said on Wednesday night: “Once the first round of voting is out of the way you will very quickly see other candidates folding because they will have one eye on a Cabinet job.
“They will come to terms with the fact they can’t win and they will back another contender to maximise their chances of a plum role in a future government.
“They will realise that the longer they carry on trying to fight against Boris or the other candidates, the less chance there is that they will be rewarded when this is all over.”
Earlier, Mr Hammond, speaking at a Bloomberg event in London, said it was not “sensible” for candidates to “box themselves into a corner” by promising Britain would leave the EU by October 31.
But his prediction that “Parliament will not allow a no-deal exit from the EU” was undermined when eight Labour MPs voted with the Government to keep no deal on the table and only 10 Tories rebelled.
Mr Javid, the Home Secretary, became the last of the candidates to launch their leadership bid on Wednesday, saying Mr Johnson was “yesterday’s news” and the party needed someone who represented the future.