LONDON • The six Conservatives vying to become Britain's prime minister were set to face off in the second round of voting yesterday, with the final pair to be decided by the end of the week.

The outcome of the leadership battle could determine under what conditions Britain leaves the European Union. Britain is scheduled to leave on Oct 31.

All of the party's 313 MPs can take part in the secret ballot in the contest to replace outgoing leader Theresa May, with further rounds scheduled to whittle the list down to the final two, who will face the party's 160,000 grassroots members.

Mr Boris Johnson, former foreign minister and leading Brexit campaigner, won the first round of voting last week, with the support of 114 MPs.

He has said he is open to leaving the EU on Oct 31 without a formal deal between London and Brussels but would prefer to secure one by the deadline.

Opponents of "no-deal" say it would cause economic chaos as Britain breaks up with its top trading partner.

Any candidate failing to win the support of at least 33 MPs yesterday would have been eliminated, with the worst-performing contender dropping out if they all reach the threshold. The result was to be announced around 6pm London time (1am Singapore time today).

Two hours later, the remaining candidates will do battle in a BBC televised debate, following a first TV showdown last Sunday which Mr Johnson skipped.

Another round of voting is scheduled today and two more tomorrow, if required, to get the numbers down to a final two.

Then party members will pick the winner in a postal ballot, with the victor set to be announced in the week of July 22.

Foreign Secretary Jeremy Hunt finished second in last week's vote, on 43, with Environment Minister Michael Gove on 37, Brexit hardliner Dominic Raab on 27, Interior Minister Sajid Javid on 23 and International Development Secretary Rory Stewart on 19.

There are 50 votes to play for that went to four contenders who have now dropped out.

Mr Stewart, an unconventional outsider, told BBC Radio yesterday that he had "no problem" with being seen as the "stop Boris" candidate.

In Sunday's sometimes ill-tempered Channel 4 debate, four of the five candidates said they would seek to renegotiate the draft Brexit deal agreed with Brussels even though EU leaders have repeatedly ruled this out.

But Mr Stewart said he would press ahead with the current agreement even though it has been rejected by Parliament three times this year.

The other candidates said they would be willing to lead Britain out of the EU without a deal on Oct 31.