Boris Johnson has launched his bid for the Tory crown with a warning to MPs they will “reap the whirlwind” if they try to thwart Brexit.

Labour said it would continue to fight to prevent a no-deal Brexit after the latest cross-party attempt by MPs to take control of Commons business was narrowly voted down.

Earlier, at his official campaign launch, Mr Johnson said both the main parties faced an “existential threat” unless Britain left the EU by the latest deadline of October 31.

“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,” Mr Johnson said.

“I think if we now block it, collectively as parliamentarians we will reap the whirlwind and we will face mortal retribution from the electorate.”

In the Commons, the cross-party motion which would have enabled MPs to take control of the business of the House on June 25 was defeated by 309 to 298 – a majority of 11.

Ten Tories, including Ken Clarke, Sir Oliver Letwin, Justine Greening and Dominic Grieve, supported the motion but eight Labour MPs voted against.

Shadow Brexit secretary Sir Keir Starmer said it would have acted as a “safety valve” enabling Parliament to pass legislation preventing the next prime minister from taking Britain out of the EU without a deal.

He said Labour would continue to work to find parliamentary mechanisms to ensure whoever succeeds Theresa May could not simply leave with no-deal in the autumn.

Sir Keir Starmer said Labour would continue to fight to prevent no-deal (Dominic Lipinski)

“This is a disappointing, narrow defeat. But this is just the start, not the end of our efforts to block no deal,” he said.

“Any Tory leadership candidates should know that Parliament will continue to fight against no deal.”

Mr Johnson, seen as the clear front runner in the contest, said it was essential that Britain was out of the EU by the end of October.

He insisted he was not aiming for no-deal, but said the Government had to show it was serious about leaving if it was to stand any chance of securing concessions from the EU.

“It is only if we have the guts and the courage to get ready for it (no-deal) that we will carry any conviction in Brussels to get the deal that we need,” he said.

His comments prompted a warning from Chancellor Philip Hammond that it would be “impossible” to leave by October 31 as the EU would not re-negotiate and Parliament would not allow it.

“I don’t think it’s sensible for candidates to box themselves into a corner on this,” he said. “I don’t think it will be in our national interest that we drive towards this cliff-edge at speed.”

Sajid Javid, the last of the 10 candidates to launch his campaign ahead of Thursday’s first round of voting, dismissed Mr Johnson as “yesterday’s news”, saying the party needed to show it had changed.

“If we’re trying to connect with the next generation and move forward as a country then I think it’s time for the next generation with a bold new agenda,” the Home Secretary said.

“That means understanding that we cannot call ourselves a ‘one nation’ party, if there are whole swathes of this country that don’t think that we share their values and their needs.”

Sajid Javid
Sajid Javid said the Tories need to show they have changed (Rick Findler/PA)

At his launch event, Mr Johnson had to fend off a series of reporters’ questions about his past character and record in office.

After Michael Gove’s admission that he had taken cocaine in the past, Mr Johnson sidestepped a question as to whether he had also used the drug.

He acknowledged that his use of language – such as his description of Muslim women who wore the burka as letter boxes – sometimes resulted in “some plaster coming off the ceiling”.

However, he rejected past charges of untrustworthiness levelled at him by colleagues and rivals.

Referring to his record as mayor of London, he said: “I do what I promise to do as a politician.”