Boris Johnson will face Foreign Secretary Jeremy Hunt in a run-off to become Britain's next leader after a final ballot of MPs on Thursday, with the winner tasked with guiding the country through Brexit.
In the fifth round of voting, former foreign minister Johnson secured the support of 160 out of 313 Conservative lawmakers, while his successor and rival Hunt won 77.
Johnson, a former London mayor, said he was "deeply honoured" to have such emphatic backing from his colleagues.
"I look forward to getting out across the UK and to set out my plan to deliver Brexit, unite our country, and create a brighter future for all of us," he tweeted.
Environment Secretary Michael Gove, who with Johnson had led the successful 2016 referendum campaign to leave the European Union, was narrowly eliminated after winning 75 votes.
The contest to replace Theresa May as prime minister will now move to around 160,000 grassroots Conservative party members, with the winner installed in Downing Street before the end of July.
Both Johnson and Hunt have promised to take Britain out of the EU as quickly as possible, with the current exit date - after two delays - set for October 31.
Both say they want to renegotiate the deal May has already struck with Brussels, which parliament has rejected three times, but are prepared to walk away if necessary.
However, the EU has repeatedly said it will not change the text and the tough talk of "no deal", particularly from Johnson, has sparked frustration across the bloc.
EU losing patience
As the result was announced in the House of Commons, May attended her final formal EU summit in Brussels, where the bloc's leaders warned her successors what to expect.
"Some of my colleagues have lost their patience," said Irish Prime Minister Leo Varadkar.
Hunt has suggested he might delay Brexit for a short time if a deal with Brussels was close, and Johnson has refused to guarantee leaving on October 31.
Former UK foreign minister Boris Johnson says he can lead Britain out of the EU by October 31. Source: AAP
But Varadkar said there was "enormous hostility" to a delay, saying it might only be acceptable to facilitate a snap election or even a second Brexit referendum.
Luxembourg's Prime Minister Xavier Bettel, one of Britain's most vocal critics, warned no alternative deal was on the table.
May announced her resignation last month after it became clear she had lost the support of her Conservative MPs and could not get her Brexit deal through parliament.
Johnson was the frontrunner from the start and despite his history of gaffes, has barely put a foot wrong in the campaign.
Critics say this is because he has limited his public and media appearances, ducking one of two live television debates.
Both he and Hunt must now face the scrutiny of members at 16 hustings around Britain.
Both men have been accused of failing to explain how they will break the Brexit deadlock in just a few short months.
Business leaders are deeply alarmed by any talk of "no deal", which the Bank of England warned on Thursday was a rising risk.
Johnson is a divisive figure, accused of populist rhetoric and a lack of attention to detail that led to an underwhelming two years as Britain's foreign minister.
But he has wooed Conservative MPs with a promise that only he has the big personality to break the Brexit deadlock and, if necessary, win a snap election.
The smooth-talking Hunt is a more traditional foreign minister, although his supporters insist that beneath his easy manner is a tough negotiator.
Critics accuse him of an inconsistent approach on Brexit, simultaneously warning of the perils of "no deal" while refusing to take it off the table.
Responding to the result, Hunt tweeted: "I'm the underdog - but in politics surprises happen as they did today.
"I do not doubt the responsibility on my shoulders - to show my party how we deliver Brexit and not an election, but also a turbo-charged economy and a country that walks tall in the world."
