UK banks will lose unfettered access to the European Union's single market when Britain leaves, meaning they will need a new or expanded banking licence from the ECB to continue offering their services in the bloc.

Angeloni said Brexit will require greater cooperation between the ECB and UK watchdogs, citing the Bank of England's supervisory arm, the Prudential Regulation Authority (PRA).

"With the PRA we will work in the coming months on a comprehensive memorandum of understanding, covering aspects such as information exchange and the reciprocal treatment of cross-border banking groups," he told an audience of bankers.

Britain's plan to leave the European Union was up in the air on Monday after Prime Minister Theresa May abruptly decided to pull a parliamentary vote on her Brexit deal.