FILE PHOTO: A river boat cruises down the River Thames as the sun sets behind the Canary Wharf financial district of London, Britain, December 7, 2018. REUTERS/Simon Dawson/File Photo

LONDON (Reuters) - Britain's banks face a hit of up 25% to their earnings if Britain crashes out of the European Union without a deal, analysts at Citigroup C.N said in a research note.

The economic slowdown that would result from a no-deal Brexit, as well as the likelihood of lower interest rates and borrowers defaulting on loans, would hit earnings per share by between 15 to 25%, the analysts at Citi wrote in the note published on Thursday.

The research is one of the most concrete assessments yet of the impact of no-deal on Britain’s banking sector, which has thus far shown few signs of the impact of Brexit other than declining confidence among business and retail customers.

Royal Bank of Scotland RBS.L on Aug. 2 said deteriorating economic conditions before Brexit were likely to derail next year's profitability, and that some customers were already struggling.

The impact of a no-deal scenario on the shares of big British lenders Barclays BARC.L, HSBC HSBA.L, Lloyds LLOY.L, RBS RBS.L and Standard Chartered STAN.L could be more muted, the Citi analysts said, as the risks of that outcome are already partly priced in.

The FTSE index of banks in Britain .FTNMX8350 has fallen 7% this year, as lenders grapple with pressure on profits from competition in the mortgage sector, ultra-low central bank interest rates and high fixed costs.