European banks will still be able to use derivatives clearinghouses in London if the Brexit negotiations run deep into next year, according to the bloc's top financial-services policymaker.

The finance industry has warned of an exodus as early as next month unless the European Union (EU) grants an extension. A previous arrangement to allow trading clients in the bloc to clear transactions in the U.K., known as "equivalence," is due to expire in March.

"Regrettably, the risk to financial stability has not yet been fully removed because industry has not so far fully prepared for a no-deal Brexit," Valdis Dombrovskis, the EU's commissioner in charge of financial services, said in a speech in London. "Therefore, I intend to propose to renew this time-limited equivalence decision beyond that date, to prepare for any eventuality."