Brexit could put the country on "a fast track to financial jeopardy," an official of the British Bankers' Association (BBA) has warned.
Major banks are already preparing to leave Britain, BBA chief executive Anthony Browne said Saturday.
"Many smaller banks plan to start relocations before Christmas; bigger banks are expected to start in the first quarter of next year," Browne wrote in a commentary published on The Observer newspaper.
Most international banks are getting prepared to move operations out of Britain, he added.
After divorcing the EU, Britain's banking sector could be crippled by additional trade tariffs and the invalidation of the legal rights of banks providing services, said Browne.
Although the BBA has asked British authorities to negotiate, other EU countries insisted the policy should be "as hard as possible for banks based in the UK," Browne said.
French President Francois Hollande said on Friday at an EU summit that negotiations will be hard if Britain wants a hard Brexit.
Other European countries could take advantage of Brexit as they want to attract jobs from London, Browne noted, adding that they might "try to use the EU exit negotiations to build walls across the (English) Channel to split Europe's integrated financial market."
He went on warning that for the wider European economy, the financial influence of Brexit could impede fundraising for investment and trade talks among countries in the region.
According to Browne, transition arrangements should be made as soon as possible. He also stressed that it is the responsibility of all European countries to ensure no barrier would be put up across the English Channel.
Britain voted to leave the EU on June 23, with negotiations with EU expected to begin at the end of March 2017.
