Boris Johnson has said it is “eminently feasible” for the UK to leave the EU on 31 October as he and his leadership rivals were asked to guarantee that the latest Brexit deadline is met.
In a live BBC TV debate, the former foreign secretary said there would be a “catastrophic loss of confidence in politics” if the deadline was not met.
Both Michael Gove and Jeremy Hunt said they could seek extra time for a deal.
But Rory Stewart said it was not realistic to do this in time.
The five men vying to be Conservative Party leader – and the UK’s next prime minister – are taking part in a live televised debate on BBC One.
They are facing questions from members of the public about whether they can guarantee Brexit will happen by 31 October, and whether a no-deal exit can be avoided.
Former Brexit Secretary Dominic Raab was earlier eliminated in the second round of voting, when Conservative MPs voted by secret ballot in the latest stage of the contest.
No deal Brexit a ‘last resort’
Mr Johnson, who is taking part in his first debate of the campaign, said the British people were “fed up” with the deadlock and the Tories would pay a “serious price” if this continued.
The frontrunner in the contest said “none of us want a no-deal outcome or a disorderly Brexit” but it was right to prepare for one to try and secure a better deal.
Sajid Javid said a deadline was needed to “focus minds”.
He suggested the only route to get a Brexit deal through Parliament was by re-packaging Theresa May’s Withdrawal Agreement but without the controversial Irish backstop.
Mr Hunt said he would back a no-deal exit as a “last resort” but if the UK was close to finalising a deal with the EU it would be wrong to leave without an agreement.
Mr Gove said an “arbitrary” deadline was counter-productive, comparing the extra time that might be needed to talk to Brussels with added time at the end of a football match.
Mr Stewart said none of the other candidates had explained how they would get a Brexit deal through Parliament.
He suggested he was seeking the most realistic “door” out of the EU while “everyone else was staring at the wall and saying believe in Britain”.
He insisted would not allow a “damaging and unnecessary” no-deal exit.
Candidates quizzed about other priorities
Moving beyond Brexit, the candidates clashed over their economic plans and whether to prioritise higher spending on public services or tax cuts.
Mr Gove said Mr Johnson’s plans to give a tax cut to those earnings more than £50,000 a year – by lifting the point at which people pay the highest rate of tax – were a mistake.
Instead, he said the focus should be on increased schools spending.
Mr Hunt called for increased spending on care for the elderly, suggesting cuts to social care budgets under the current Tory government went “too far”.
Mr Stewart said the current state of the social care system was a “disgrace” and a “revolution” was needed in provision, not mere tinkering. He said promising tax cuts were “wrong” given the uncertainty around Brexit.
But Mr Gove said “bringing people together was not enough” and Mr Stewart did not have a plan for the UK after Brexit.
Mr Javid said tax cuts could generate extra revenues and make the economy more dynamic.
Challenge over Islamophobia
Mr Javid also said politicians should be “brave enough” to call out Islamophobia and other forms of racism, even if they originated from the US President Donald Trump.
He called for all the other candidates to agree to an external inquiry into Islamophobia in the Tory Party.
The BBC received thousands of questions ahead of the debate, with the largest number being about Brexit. Other topics submitted included HS2, public spending and climate.
The programme team selected the questions to be asked after making an editorial decision on the ones that best represent the issues likely to face the next prime minister.
The BBC said the questions will come from a cross-section of society, not necessarily all Conservative voters.
How can you watch the debate tonight?
Our Next Prime Minister is being hosted by BBC Newsnight presenter Emily Maitlis and broadcast on BBC One at 20:00 BST.
You can also follow the debate on our live page on the BBC News website.
Alternatively, you can stream the debate online through BBC Sounds or by watching BBC One and the News Channel through iPlayer.
From 21:00 BST, the BBC News Channel will be broadcasting reaction to the debate from politicians and pundits.
The debate is also being broadcast live on Radio 4.
Tory leadership race: BBC debate gets under way}