Drug chase sparks off row over Gibraltar
The Government has accused Spain of "a clear violation of UK sovereignty" by sending boats and helicopters into British waters in Gibraltar.
Ministers said repeated incursions are "completely unacceptable and unlawful under the international law" and pledged to urgently raise the matter with the Spanish.
The row broke out after Spanish state vessels chasing suspected drug smugglers made several forays into waters around Gibraltar in the past two days.
The Royal Navy escorted the Servicio de Vigilancia Aduanera (SVA) - the Spanish drugs and money laundering squad - out of the waters following the row.
Foreign Office Minister Hugo Swire said: "We understand that the Spanish were in pursuit of vessels who may have been committing crimes.
"However, it is completely unacceptable and unlawful under the international law of the sea to enter our waters without notifying us."