The governor of the Bank of England, Mark Carney, has warned that most businesses are unprepared for a no-deal Brexit as he called for a transition period to be agreed.

Carney was speaking after he released analysis suggesting the UK would be tipped into a recession worse than the 2008 financial crisis if it quit the EU next March with no agreement in place.

His concerns were echoed by the main financial regulator, the Financial Conduct Authority (FCA), which said it might not be able to protect the City from suffering serious setbacks without a transition period.

Carney told BBC Radio 4’s Today programme: “We know from our contacts with business, others know from their contacts, that less than half of the businesses in the country have initiated their contingency plans for a no-deal Brexit.

“All the industries, all the infrastructure of the country, are they all ready at this point in time? As far as we can tell, the answer is no.”

Since releasing its assessment of a no-deal Brexit and how it would compare with a settlement similar to the one negotiated by Theresa May, the governor has come under fire from Brexit-supporting MPs for appearing to back the Treasury’s “project fear” campaign.

Carney said those who accused the Bank of scaremongering, after it said no deal would result in an 8% cut in GDP, soaring unemployment and house prices falling by almost a third, were wrong.

He said: “We have a responsibility to have systems ready for whatever happens.”

Asked what type of Brexit he would like to see, Carney said he did not have a preference, other than to see a transition period agreed.

“It is advisable to have a transition to whatever form of Brexit parliament chooses. From a financial system perspective, something in the 18 to 24 months [range] is sufficient,” he said.

The FCA said a no-deal scenario could lead to “significant challenges” and cautioned it could not guarantee to mitigate all of the risks, given this also required action from EU authorities, “which has so far not happened”.

In a 30-page Brexit scenario report, the regulator said “consumers could potentially be affected if firms are unable to continue providing services or as a result of wider economic or market disruption”.

The regulator added markets would continue to function though “some market volatility is to be expected in this scenario”.