Britain's biggest banks are preparing to move out of the country in early 2017 because of fears over the impending Brexit negotiations, while smaller banks are making plans to leave before Christmas, the chief executive of the British Bankers' Association Anthony Browne said.

"The public and political debate at the moment is taking us in the wrong direction," the Observer Sunday newspaper quoted Browne as saying in an interview.

The paper released a short extract on Saturday evening but no further comments by Browne from the interview were immediately available.

Banks in Britain depend on a European "passport" to serve clients across the 28-country European Union from one base and lenders worry that this right will end after Britain leaves the EU.