Mr Johnson has been noticeably absent from the leadership campaign, leading some to believe he is being "hidden" to avoid making any gaffes.
But he appealed to supporters today to back him so he can deliver Brexit - with or without a deal - by 31 October, saying that "now is the time to unite the country".
Britain's Queen Elizabeth II talks to London Mayor Boris Johnson during the Beijing Olympics Team GB reception at Buckingham Palace in London.
Boris Johnson watches the election results with his wife Marina (L), at the count in Watlington, Oxfordshire, after winning the Henley seat for the Conservatives in the 2001 General Election. The seat was Michael Heseltine's, who has stepped down at this election.
Spectator editor and Conservative MP Boris Johnson (left) chats to former Tory Chancellor Lord (Norman) Lamont at a party to mark the Spectator's 175th anniversary, at the Four Seasons Hotel, Park Lane, London. Among those also in attendance at the party were Home Secretary David Blunkett, broadcasters David Dimbleby and Andrew Neil, and TV chef Nigella Lawson.
Boris Johnson, Conservative MP and editor of The Spectator magazine, at a party to mark The Spectator's 175th anniversary, at the Four Seasons Hotel, Park Lane, London. Among those also in attendance at the party were Home Secretary David Blunkett, broadcasters David Dimbleby and Andrew Neil, and Ulster Unionist leader David Trimble. 16/10/2004 The Spectator editor Johnson, has been ordered by Tory leader Michael Howard to go to Liverpool to apologise for an article in his magazine accusing its people of 'wallowing' in their 'victim status'. Mr Johnson, who is also the Conservative shadow minister for the arts, said he would be travelling to the city next week in a 'spirit of complete humility' to apologise in person for the offence caused.
Shadow Arts Minister Boris Johnson campaigns for donations from delegates at the Conservative Party Annual Conference in Bournemouth. 15/10/2004: Tory MP Boris Johnson who edits The Spectator magazine where a leading article has accused Liverpudlians of wallowing in what they regard as their "victim status" over the murder of Ken Bigley and the Hillsborough football disaster in 1989.
Conservative Party MP Boris Johnson sits through a series of speeches during the Conservative Party Conference in Bournemouth.
Boris Johnson MP (centre) and editor of the Spectator at the Liverpool Institute for Performing Arts during a visit to the city to apologise for remarks made in his magazine about beheaded hostage Ken Bigley and the Hillsborough tragedy. But council leaders called on the people of Liverpool to ignore the "Boris Johnson show". The Tory MP for Henley created a storm of protest after the publication of a leader written in the Spectator, which suggested Liverpudlians were "hooked on grief".
Boris Johnson MP and editor of the Spectator magazine arrives at Claridges Hotel in London, where he is hosting the 'Spectator Parliamentarian of the Year' Awards. 13/11/2004 Boris Johnson who was Saturday November 13 2004, sacked from the Conservative frontbench amid fresh allegations about his private life, a spokesman for Tory leader Michael Howard said.
Boris Johnson arrives at his house in north London, after going for an early morning jog. The former Shadow Arts Minister and Deputy Chairman of the Conservative Party, was relieved of his position by party leader Michael Howard, after revelations about his private life were published in a tabloid newspaper.
Boris Johnson, MP for Henley and Conservative spokesman on Higher Education, opens a footpath at the Environments Agency in Wallingford, Oxon, Friday April 7 2006. He later started a race between a car, a cyclist, runners and walkers to promote green travel. Watch for PA story.
England's Boris Johnson and Germany's Maurizio Gaudino shake hands at the end of the game
England's Boris Johnson (L) tackles Germany's Maurizio Gaudino during the Legends match at the Madejski Stadium in Reading.
Shadow education spokesman Boris Johnson MP, attends the final day of the Conservative Party's Annual Conference in Bournemouth.
Boris Johnson MP addresses a group of sixth form students from schools across London after being handed a petition against plans to scrap the last remaining ancient history A-level outside the House of Commons, London.
Boris Johnson (left) joins the Save our Services campaign against health cuts at St, Mary's Hospital in Sidcup, Kent.
Candidates for Mayor of London, Labour's Ken Livingston (left), Lib Dem candidate Brian Paddick (centre) and Boris Johnson of the Conservative party, appear together on television debate.
Conservative candidate for Mayor of London Boris Johnson launches the final phase of his mayoral campaign at Bounces Road Community Hall, North London today.
Conservative Party leader David Cameron congratulates Boris Johnson on becoming London Mayor at Tory HQ in central London.
Newly elected London Mayor Boris Johnson wears a policeman's hat in Trafalgar Square, central London during the Sikh New Year Festival celebrations of Vaisakhi.
Mayor of London Boris Johnson waves the Olympic Flag during the handover ceremony as President of IOC Jacques Rogge (centre) and Mayor of Beijing Guo Jinlong look on at the National Stadium during the 2008 Beijing Olympic Games, China.
Retired Formula 1 World Champion Mika Hakkinen (right) and current Formula 1 World Champion Lewis Hamilton (left) join Mayor of London Boris Johnson in backing an anti-drink-drive campaign at Potters Fields Park in London.
London Mayor Boris Johnson (2nd Left) celebrates St Georges Day in Leadenhall Market in the City of London today where he saw a festival of English food and drink.
Leader of the Conservative Party David Cameron (2nd right) with Mayor of London Boris Johnson (2nd left) as they celebrate St George's day in Leadenhall Market in the City of London.
Boris Johnson and TV star Kelly Brook launch the Mayor of London's Skyride, Peter's Hill steps, London.
London Mayor Boris Johnson with a sculpture of a blue cockerel as he unveils the next two commissions for the fourth plinth in Trafalgar Square, which includes the cockeral (pictured) by Katharina Fritsch and a boy on a rocking horse named Powerless Structures by Michael Elmgreen and Ingar Dragset.
Boris Johnson pictured with members of the Genesis Mas band, who will be performing at the Notting Hill Carnival this weekend, at Potters Fields in central London.
Mayor of London Boris Johnson (left) with Prime Minister David Cameron during the lighting of the Paralympic Cauldron in Trafalgar Square, central London.
London Mayor Boris Johnson boards one of the first trains of the new London Overground extension connecting Clapham Junction with Canada Water. ASSOCIATION Photo. Picture date: Monday December 10 2012. The new service will be London's first new orbital Journey times from south and east London. See PA story RAIL Link. Photo credit should read: Stefan Rousseau/PA
Actor Brian Blessed (left) and Mayor of London Boris Johnson sell poppies in Liverpool Street Station in central London with they collected money from commuters including nine year old Arthur Crowley (centre) from Salisbury.
Mayor of London Boris Johnson (centre) swings from a bus as Northern Ireland Secretary Theresa Villiers (left), Northern First Minister and DUP leader Arlene Foster and Minister of Enterprise, Trade and Investment Jonathan Bell (second right) look on during a visit to Wrightbus Chassis plant in Antrim.
Foreign Secretary Boris Johnson (left) and his Russian counterpart Sergei Lavrov during a press conference following their meeting in Moscow.
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He said that around the country there was "moral despair" that MPs had not yet implemented Brexit, but he said he "did not want" to leave without a deal - but would prepare for it.
Mr Johnson said "now was the time to remember our duty" when it came to the results of the EU referendum.
He told guests: "The commercial dynamism of the British people is insulating them from the chaos of British politics."
He went on: "We simply will not get a result if we give the slightest hint that we want to go on kicking the can down the road with yet more delay.
"Delay means defeat. Delay means Corbyn. Kick the can and we kick the bucket."
"We have made tensions worse with delay. When we come up with that better deal there will be a relief that Brexit is off the front pages...
"If we are to respond to the profound message of that Brexit vote then we must fight now for those that feel left behind."
In a withering attack on Labour leader Jeremy Corbyn, Mr Johnson said: "He and what he stands for are a real threat to our fundamental values and way of life."
Following the speech, Mr Johnson was asked if he was keeping a no deal Brexit on the table.
He said: "Yes of course. It's right for our country to prepare for that outcome. What most people understand is that the best way to avoid a no-deal outcome and a disorderly Brexit is to make the preparations now so we can leave in a managed way if we have to.
"We will carry the conviction with our friends and partners that we can make such an exit if we have to, which would be a last resort.
"That is the way we'll get a deal that is sensible for both sides of the Channel. We will engage in the friendliest possible way with our friends across the Channel... a new optimism and confidence in what Britain can do, and I think they'll respond to that.
"It isn't good for the UK or our partners to continue with this uncertainty. It's important to be robust and committed now."
Questioned over his description of Muslim women as "letterboxes", Mr Johnson responded: "Of course occasionally the plaster comes off the ceiling as a result of a phrase I've used.
"It's vital we as politicians remember the reasons the public feel alienated from us is we feel we're muffling and veiling our language, not speaking as we find, when what they want to hear is what we genuinely think.
"If in doing that I sometimes cause offence I apologise, but I'll continue to speak as directly as I can."
Asked if he had done anything illegal, Mr Johnson said he had "not always observed the 70mph top speed limit in this country".
Mr Johnson swerved further questioning on his cocaine use while at university, saying: "The canonical account of this has appeared many many times and what people in this country want us to focus on is what we can do for them and what out plans are for this country... all the rest of it is in danger of blowing us off track."
Asked about how he would deliver a no-deal Brexit if it was blocked by Parliament, Mr Johnson said that he believed "maturity would prevail".
He added: "A sense of duty will prevail. It will be very difficult for colleagues in parliament to obstruct the will of the people and block Brexit."
A smattering of anti-Brexit protesters gathered to picket outside the venue for Mr Johnson's campaign launch in central London, while shouts of "Stop Brexit" could be heard from outside the room during the speech.
Attendees at the launch were offered "Boris bacon butties" and "Boris eggs Benedict" inside the venue.
They were also invited to wear "Back Boris" badges.
With 80 Tory MPs already backing the former Foreign Secretary, he currently stands as the favourite to take over from Theresa May next month.
While Mr Johnson has proved popular with many MPs, he nevertheless remains a divisive figure in his own party.
Ahead of his launch, Cabinet minister Liz Truss defended the former London Mayor as a "brilliant" Foreign Secretary who deserves to be PM.
Chief Secretary to the Treasury Ms Truss attempted to bat away a string of criticisms about how Mr Johnson may not be a fit and proper person to hold office.
When the accusation that Mr Johnson was "the worst Foreign Secretary in living memory" was put to her by the BBC Radio 4 Today programme, she said such attacks were due to his "huge public appeal".
She said: "I think it's a sign - that he is being attacked shows the huge public appeal he has, the huge power he has to communicate.
"His record is of being the most successful mayor of London we have had, of being an excellent foreign secretary who got countries around the world to take action against Russia by expelling their diplomats."
Ms Truss also defended Mr Johnson when asked about his sacking for "lying in public" about an affair, saying: "I do not think the British public is interested in Boris's personal life."
Defending the Tory leadership hopeful from accusations that he is refusing to speak to journalists during his campaign for the top job, she said: "He has got nothing to hide.
"This is the parliamentary stage of the process. The important thing is he is talking to parliamentary colleagues."
Mr Johnson's path to securing Brexit may hit a major stumbling block before a new PM is even voted in as Parliament is set to vote on Labour's plans to stop leaving without a deal later today.
Mr Johnson's potential stumbling block could force him to hold a snap election shortly after entering Downing Street.
A new poll shows that the Tories would win a thumping majority if Mr Johnson was in charge during an election - meaning he may be persuaded to take Brexit to the country in a General Election.