London: The Spanish government was accused on Sunday of committing an “outrageous” violation of British sovereignty by sending boats and helicopters into UK waters in Gibraltar.

Gibraltar’s chief minister said he was “astonished and appalled” after Spanish police chasing criminals made several incursions into British waters over the past two days. The Royal Navy helped escort the Servicio de Vigilancia Aduanera (SVA) — the Spanish police’s drugs and money laundering squad — out of the waters following the international row. Chief minister Fabian Picardo said the incursions amounted to an illegal and dangerous display of “bravado”.

He said: “I am sure I am speaking for the whole of Gibraltar when I say that we consider this has been a serious and unnecessary failure on the part of the Spanish SVA, which has had outrageous consequences in respect of the violation of our sovereignty.”

In one incident, the Spanish are understood to have been pursuing smugglers who were dumping suspected bales of drugs off the side of a fast-speed inflatable boat when they travelled through British waters. They also allegedly flew a helicopter over the Sandy Bay beach area of the island in a move branded “extremely dangerous” by the Gibraltan government. In another incident the Spanish allegedly boarded a boat and questioned crew.

Picardo said police in Gibraltar should have been asked to assist in catching the criminals once the chase looked like it would go into British-controlled waters. He blamed the failure to do so for the escape of one suspected drug smuggler. “Its actions have ultimately resulted in the escape of a criminal that citizens on both sides of the frontier would have liked to have seen arrested and imprisoned for his drug trafficking.

“We all want to stop the drug smugglers. It beggars belief that the SVA have acted in this way that, in effect, has allowed a criminal who should be behind bars to get away. The whole of Gibraltar will be outraged at their failure to cooperate in a way that would have better assisted to capture the criminals in question.”

Picardo said he expected British ministers to pursue the matter.

Spain disputes UK sovereignty over Gibraltar, which has been controlled by Britain since 1713. British Foreign Office minister Hugo Swire said: “On 9 August, Spanish state vessels repeatedly entered British Gibraltar territorial waters without notifying Gibraltarian authorities. 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.

“These repeated incursions into British Gibraltar territorial waters are a clear violation of UK sovereignty by another EU country and we will be raising this as a matter of urgency with the Spanish authorities.”

In October last year, the British government expressed its “grave concern” over manoeuvres carried out by a Spanish research vessel off Gibraltar. The Foreign Office said that the Angeles Alvarino provoked the Royal Navy into acting, thereby putting the lives of personnel at risk when it entered British waters. There was a stand-off as Royal Navy vessels circled the ship.

Europe minister David Lidington said at the time: “The irresponsible actions and dangerous manoeuvring of this vessel were not only unlawful but also presented a significant risk to the safety of Royal Navy personnel at sea.”