LONDON — British police commissioners are warning that a sharp break from the European Union may put the public at risk.

The Association of Police and Crime Commissioners warns in a letter released Tuesday that leaving the EU without an agreement on future relations would mean "a significant loss of operational capacity" because police would instantly lose access to cross-border investigative powers and databases.

The association, whose members are elected officials responsible for policing in England and Wales, says these concerns come as the threat from foreign nationals targeting the U.K. from abroad is increasing.

Tensions are rising as Britain tries to hammer out an agreement by October that can be approved by all the EU member states before the U.K. leaves the bloc on March 29.