The Bank of England governor, Mark Carney, says food prices could rise between 5% and 10% if there is no orderly Brexit plan.
Mr Carney told a committee of MPs that in the most “extreme” scenario, prices would go up by 10%, but in a more orderly scenario by more like 6%.
The Bank of England and its governor have attempted to assess the impact of Brexit on several occasions.
All its assessments have seen it as a potential negative.
Mr Carney’s colleague, Sir Jon Cunliffe, said the UK imported about half of its food from overseas. The price rises would come partly from a fall in the value of the pound, partly from any tariffs imposed and partly from increased costs at the border as these were checked.
He and senior bank colleagues were also challenged by MPs over what some critics have called scaremongering over Brexit.
Mr Carney said they had put a lot of work into the assessments: “There’s no exam crisis. We didn’t say up all night.”
He said a core team of 20 senior economists worked on it for a couple of years, 150 different professionals across the Bank were also drawn in and then the report was reviewed by both the Monetary Policy Committee and the Bank’s Financial Policy Committee.
Last week, Mr Carney said that fewer than half of businesses had initiated contingency plans.