The governor of the Bank of England Mark Carney has warned that a no-deal Brexit would be an instant shock for the British economy.
A day after the regulator said there was a one in three chance of Britain falling into recession, Mr Carney said a "substantial" number of companies stood to be affected by a no-deal scenario.
"With no-deal the shock to the economy is instantaneous and instantly.... you actually have businesses that are no longer economic," he told BBC's Today programme.
Mr Carney added he was still expecting a deal with Brussels, but warned there was "a significant possibility" that Britain could leave the EU without a divorce agreement.
"There are some very big industries in this country where that which is highly profitable becomes not profitable, becomes not economic" in case of no-deal, he said.
He said the automotive, transport, food and chemical sectors would face the biggest challenges in the event of a no-deal Brexit, adding that very difficult decisions need to be taken."
Yesterday, the Bank of England lowered its growth forecasts but left interest rates unchanged at 0.75%.
It said it was less confident about its outlook for the British economy because of Brexit and noted that the increased risk of a disorderly Brexit had led to a "marked depreciation" in sterling.
Brexit supporters say Carney is overly pessimistic about Britain's future outside the European Union.
Former Conservative Party leader Iain Duncan Smith said he was "one of the architects and promoters of Project Fear" in comments published in the Daily Telegraph today - a charge Mr Carney denied.
"It ... is not helpful to deny that shifting from the most integrated economic relationship in the world, which is being a member of the European Union, to a new relationship that is potentially just WTO relationship ... that that would not have an effect on the economy," Mr Carney said.
