Brexit will take place on 31 October "whatever the circumstances", Downing Street has said, refusing to say whether Boris Johnson would regard a vote in parliament against a no-deal departure as sufficient reason to change course.

Quizzed repeatedly at a media briefing, the prime minister's spokesman also declined to say whether the government would consider allowing no deal to happen if it were amid an election campaign, or if Johnson lost a no-confidence vote in the Commons.

The spokesman said he could not comment on hypothetical situations. But asked whether, as a matter of broader principle, Johnson could commit to respecting votes in parliament, he also declined to answer.

He pointed out that a no-deal departure was simply the consequence of legislation as it stood: "The legal default, as put in place by parliament, is that the UK will leave on 31 October, with or without a deal."