Britain's finance minister on Monday,, said he did not think "anyone really knows" what a no-deal Brexit would cost the economy.

Sajid Javid spoke to BBC radio before his keynote speech at the governing Conservative Party's annual conference in Manchester.

Chancellor of the Exchequer Javid said he was not sure how much a no-deal Brexit would cost, telling the BBC: "I don't think anyone really knows a full proper answer to that question."

Prime Minister Boris Johnson insists that Britain will leave the European Union at the end of October with or without a deal.

Javid declared Monday that a no-deal Brexit "is not our preferred outcome".

He added: "We are working incredibly hard to get a deal by October 31. I absolutely believe that can still happen. It can still be done.

"But if we do not manage to do that, we do still need to leave the EU on that date. We cannot have any more dither and delay -- and we will leave, if we have to, without a deal on October 31."

Javid will later confirm plans for extra government investment in roads, buses and broadband internet.

"The full benefits of our infrastructure revolution may not be felt for some time. But the work must start here and now," he will tell delegates, according to an advance copy of his speech.

Copyright AFP. All rights reserved.

Brexit Boris Johnson
Johnson insists progress has been made in talks with the EU's Brexit team. Photo: POOL / DANIEL LEAL-OLIVAS