MANCHESTER • Former London mayor Boris Johnson and Foreign Secretary Jeremy Hunt, rivals in the race to become Britain's next prime minister, clashed on Tuesday over who could be most trusted on Brexit, in a sometimes bad-natured television debate just two weeks before one will be chosen.

With Mr Johnson in the lead to replace Prime Minister Theresa May, both were asked repeatedly to prove that they would take Britain out of the European Union on Oct 31 and that they would protect businesses from a no-deal Brexit.

More than three years after Britain voted to leave the bloc, Brexit is dominating the race, with both candidates trying to point out the other's weaknesses.

Mr Johnson raised questions over Mr Hunt's commitment to leaving on the Oct 31 deadline, while Mr Hunt criticised Mr Johnson for relying on what he said was nothing more than optimism to win a deal.

Mr Johnson told the debate on ITV in front of an audience: "I think it is very, very important not to envisage any circumstances in which we would fail to come out of the EU on Oct 31."

Asked repeatedly if he would quit as prime minister if Britain failed to leave by the deadline, Mr Johnson refused to answer directly, saying: "I don't want to hold out to the EU the prospect that they might encourage my resignation by refusing to agree to a deal."

That prompted Mr Hunt to accuse him of avoiding direct answers and relying on nothing more than optimism to win a new deal from the EU, or to leave without a deal which would hurt businesses across Britain.

"Because Boris never answers the questions, we have absolutely no idea what his premiership would be like," Mr Hunt said.

Conservative Party members are submitting their postal ballots to appoint the new leader of their party - and the leader of the country - who will be announced on July 23.

Before the TV debate, Members of Parliament narrowly passed a measure aimed at stopping Britain's future leader from forcing the country out of the EU without an agreement.

Former prime minister John Major said he would be willing to go to court to block a new leader from delivering a no-deal Brexit by suspending Parliament, saying that he would act to prevent the Queen from being dragged into a constitutional crisis.