The former foreign secretary has said further delays to Brexit would mean a Tory defeat at the next election. Johnson has been criticized by rivals for failing to face the public until now.
At his first public appearance since announcing his intention to run for the leadership of the Conservative Party, Boris Johnson has outlined his plans should he become prime minister.
The bookmakers' favorite to replace Theresa May said prolonged membership of the European Union would give Jeremy Corbyn the keys to number 10.
The United Kingdom has already postponed its exit from the EU on two occasions and Johnson said: "After three years and two missed deadlines, we must leave the EU on October 31."
He continued: "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."
According to the former London Mayor, opposition leader Corbyn is "a real threat to our fundamental values and our way of life."
Johnson, who has been endorsed by US President Donald Trump, said he was "not aiming for a no-deal outcome but it is only responsible to prepare vigorously and seriously for no-deal. Indeed it is astonishing that anyone could suggest dispensing with that vital tool in the negotiation."
Suggestions of leaving the bloc without an agreement in place has led to opposition politicians voting on a motion to prevent a no-deal Brexit.
Keir Starmer, Labour's Brexit Secretary, said: "The debate on Brexit in the Tory leadership contest has descended into the disturbing, the ludicrous and the reckless. None of the likely candidates for the top job has a credible plan for how to break the deadlock before the end of October."
Rivals hit out
Several of the other contenders for the leadership have spoken out about Johnson's lack of public appearances prior to Wednesday's speech.
Mark Harper and Matt Hancock have both criticized Johnson's failure to show himself until now.
Harper said all viable candidates should be open to scrutiny. "If you want to lead this country, you have to be prepared to set out your stall," he said. "I think you have to open yourself up to questioning and be prepared to level with people."
Meanwhile, Health Secretary Hancock spoke about Johnson's reluctance to take part in a possible television debate. He said: "Everybody should participate in the proposed TV debates. And I think we've got to ask the question, why not? I've got nothing to hide and that's why I am here."
Rory Stewart, an outsider in the leadership race, also questioned the former London mayor's suitability for the role.
During a public appearance, Stewart said: "Do you really feel that this is the person that you want engaging in the detail of the future of your health and education system? Is this the person you want writing the instruction to the nuclear submarines? Is this the man that you want embodying your nation and guiding you through the most difficult choice we've faced for 50 years?"
Calling out the elites
Home Secretary Sajid Javid, on the other hand, underscored his own immigrant background in making his pitch for the leadership role.
When Javid pointed to the privileged position many in Westminster were born into he said he did not begrudge them their advantage. Still, he noted: "It wasn't birth right or connections that got me to where I am today. It was hard work, public services, and family. And it is those three ideas that will lie at the heart of my bold policy agenda, a manifesto for change that will make our country fairer, stronger and more united."
Before entering politics Javid worked as an investment banker at Chase Manhattan Bank, and then as a managing director at Deutsche Bank. He left Deutsche Bank in 2009 and was first elected to Parliament in 2010. He has served in a number of Cabinet positions since 2014. The son of Pakistani immigrants, Javid was appointed home secretary in April 2018.
jsi/rc (AP, Reuters)