MPs would “reap the whirlwind” and face “mortal retribution” if they blocked Brexit, Boris Johnson, the frontrunner to succeed Theresa May, warned his and other parties at Westminster.

His warning came as MPs opposed to a no-deal Brexit prepared to launch a fresh cross-party attempt to take control of the Commons agenda to prevent Britain leaving the EU in the autumn without a deal in place.

In a leadership campaign launch in central London, Mr Johnson brushed aside journalists’ challenging questions and in some cases simply avoided answering them as he tried to keep on message; that he will deliver Brexit, deal or no-deal by October 31, and he is the only candidate who can defeat Jeremy Corbyn and Nigel Farage at the ballot box.

In a crammed room, overflowing with MPs and journalists and with a “Back Boris” backdrop, the former Foreign Secretary insisted he wanted to get a new deal with Brussels and that a no-deal outcome was a “last resort”.

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He explained: “I am not aiming for a no-deal outcome, I don’t think we can end up with any such thing. But it is only responsible to prepare vigorously and seriously[for a no-deal].

“It’s 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. Delay means defeat, delay means Corbyn, kick the can again and we kick the bucket,” declared Mr Johnson.

He took a sideways swipe at Theresa May when he said – to hear, hears from supporting MPs - he found it “astonishing” that the threat of a no-deal, which he described as a “vital tool of negotiation,” had been cast aside.

The former Cabinet minister explained how across Britain there was a “mood of disillusion, even despair” at Westminster’s inability to get things done while Brexit remained unresolved.

“The longer it goes on, the worse the risk of serious contamination and a real loss of confidence, because the people of this country deserve better from their leaders.

“Now is the time to unite this country and this society and we cannot begin that task until we have delivered on the primary request of the people, the big thing they asked us to do. After three years and two missed deadlines, we must leave the EU on October 31,” he insisted.

Mr Johnson predicted that maturity and a sense of duty would prevail, believing it would be very difficult for MPs to obstruct the will of the people and block Brexit.

“If we now block it collectively as parliamentarians, we will reap the whirlwind and we will face mortal retribution from the electorate. I just say to friends and colleagues: let’s come together and get this thing done. In Brussels, they will have a government inspired by a new vigour, confidence and optimism about what we can do but also total conviction about the way forward…

“We will get results. I’m not pretending everything will be plain sailing. There will be difficulties and there may be bumps in the road. My team will hit the ground running and work flat out between now and October 31.

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“We will get the result the country needs; a sensible, orderly Brexit that allows this country to flourish as a great, independent nation but also gives a new partnership with our friends across the Channel.”

He insisted he would fight with every fibre of his being to promote sensible, moderate, modern Conservatism and to defeat the nihilistic socialist approach of Jeremy Corbyn, who, he claimed, would destroy Britain’s way of life.

Mr Johnson insisted if he and the Tories succeeded, the “whole country will win”.

In his speech, he spoke of the gulf in prosperity between south east England and the rest of the UK and the need to unite society. He pledged that under his premiership there would be a “levelling up” to help those who felt they had been left behind.

“It should be our moral fundamental purpose as a government to bridge not just the wealth gap, not just the productivity gap but the opportunity gap between one part of the UK and another,” he declared.

The former London Mayor claimed it could be done because he had done it in the UK capital during his two terms in office at City Hall. He spoke about helping the less well-off on transport, building affordable homes, expanding the living wage and halving the murder rate.

“When you consider Britain’s calamities fall disproportionately on the poorest families you can see everything we did was driven by a desire for social justice.”

He spoke about the desire to help business create jobs while ensuring there were first class public services, referring to the “sizzling synergy” of modern Conservatism.

“So that no town, no community, no person feels left behind. That is the way we will reknit the bonds of this amazing country.”

Mr Johnson stressed in everything he would do in power would be to seek to strengthen the Union of four nations, which he referred to as the “invincible quartet, the awesome foursome, the world’s soft power superpower”.

He said the Union flag represented economic and political freedom, democracy, free speech, human rights and environmentalism.

“It’s time to end the doubts and division with clarity and decision. That’s why I believe I am the right person to take this country forward.”

Mr Johnson has thus far been accused of pursuing a “submarine” approach to the leadership contest but when he finally surfaced to take journalists’ questions about his past and about trust, he skilfully dodged them. Indeed, at the end of the campaign launch several reporters stood up to demand he take more than just a few questions.

Asked about his previous confession that he had taken cocaine while at university, the former London Mayor replied: “The account of this event when I was 19 has appeared many, many times.

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“What most people in this country want us to really focus on in this campaign, if I may say so, is what we can do for them and what our plans are for this great country of ours."

When he was asked about his controversial remarks about Muslim women looking like bank robbers and letterboxes and that those who worked with him did not believe he was fit to be PM, the questioner was met with vocal protests from supportive MPs.

To applause, Mr Johnson said he was delighted many of his colleagues appeared to dissent from the sentiment of the question.

He admitted that occasionally “some plaster comes off the ceiling” from a phrase he might have used or might have been misinterpreted by his detractors.

“But it is vital that we as politicians remember that one of the reasons why the public feels alienated now from us all as a breed is because too often we are muffling and veiling our language.

“Not speaking as we find, covering everything up in bureaucratic platitudes when what they want to hear is what we genuinely think. If sometimes in the course of trying to get across what I genuinely think, I use phrases and language that have caused offence, then, of course, I’m sorry for the offence that I have caused but I will continue to speak as directly as I can.”

Throughout the launch, a muffled voice could be heard from the street outside, shouting: “B******s to Boris!” and "Stop Brexit!"