The European Commission is to send a fact-finding mission to Gibraltar to examine the legitimacy of border controls imposed by Spain in a growing dispute over the British Mediterra-nean enclave.

It broke out after Gibraltar’s construction of an artificial reef using concrete blocks in the bay off the tiny territory. Gibraltarian authorities say the move was necessary to help marine life recover from overfishing. Spanish fishermen counter that it hampers their access to certain waters. Spain, in turn, has toughened its border checks, leading to long queues for workers and tourists entering Gibraltar.

While Spain has threatened to take its claim on Gibraltar to the United Nations, Britain last week called on the Commission, the European Union’s executive, to send in monitors to check whether Spain’s controls breach EU rules.

And yesterday, as British warships arrived in Gibraltar on a previously scheduled, routine port of call, Commission President Jose Manuel Barroso and Spanish Prime Minister Mariano Rajoy spoke by telephone.

“They agreed that a Commission fact-finding mission should as soon as possible examine in loco the border control, movement of people and goods questions,” a Commission statement said.

“President Barroso expressed his hope that Spain and the UK will address these matters in a way that is in line with their common membership in the EU.”

A Commission official said Spain is entitled to carry out border checks but these must be proportionate – a definition open to interpretation. Britain, and therefore Gibraltar, is not a member of the Schengen open border agreement between many EU states. Spain is a Schengen participant.

Although British, Spanish and Gibraltarian authorities have said the navy’s arrival at the British overseas territory was long scheduled, some in Spain regarded it as provocative.