Michael Gove, who is in charge of no-deal preparations in the Cabinet Office, said there was a "very real prospect" that an agreement would not be struck with Brussels before the deadline.

Writing in The Sunday Times, he said that while the aim was still to leave with a deal, the Government needed to prepare for every eventuality.

"With a new prime minister, a new government, and a new clarity of mission, we will exit the EU on October 31. No ifs. No buts. No more delay. Brexit is happening," he said.

"The EU's leaders have, so far, said they will not change their approach - it's the unreformed withdrawal agreement, take it or leave it," he added.

"We still hope they will change their minds, but we must operate on the assumption that they will not."

Gove said the Government would do "everything in our power" to secure a good deal for the UK, but said simply presenting Theresa May's Withdrawal Agreement to Parliament again would not be enough.

"You can't just reheat the dish that's been sent back and expect that will make it more palatable," he wrote.

Planning for no deal was now a "number one priority", he said, as the paper reported that Prime Minister Boris Johnson had put together a "war cabinet" of six key ministers to deliver Brexit by October 31 "by any means necessary".

Chancellor Sajid Javid has said there will be "significant extra funding" this week to get Britain "fully ready to leave" the EU on October 31, with or without a deal.

The additional spending will include financing one of the country's "biggest ever public information campaigns" to ensure individuals and businesses are ready for a no-deal exit, Javid told the Sunday Telegraph.

Meanwhile, polls have suggested the Tories were boosted by a "Boris bounce" after the election of their new leader.

Since Johnson became prime mMinister after being declared party chief by Tory members, the Conservatives have gained 10 points to stand at 30 per cent, a survey by Deltapoll for the Mail on Sunday showed.

That puts them five points ahead of Labour at 25 per cent, with the Liberal Democrats on 18 per cent and the Brexit Party on 14 per cent.

Australian Associated Press