Spain has long maintained that the waters surrounding the peninsula – unlike the Rock itself – were never ceded to Britain as part of the 1713 treaty of Utrecht

Britain has summoned the Spanish ambassador in London for an official rebuke after a Spanish boat crossed into waters off Gibraltar and refused multiple requests from the navy to leave.

Matthew Rycroft, one of the Foreign Office’s most senior civil servants, called in Federico Trillo on Tuesday afternoon to discuss the incident, which the UK called “provocative”.

David Lidington, Europe minister, said: “I strongly condemn this provocative incursion and urge the Spanish government to ensure that it is not repeated.

He added: “We stand ready to do whatever is required to protect Gibraltar’s sovereignty, economy and security . . . We remain confident of UK sovereignty over the whole of Gibraltar, including British Gibraltar territorial waters.”

It is the third time the British have called in the Spanish ambassador since December 2011 over such incursions. But this incident is regarded as particularly serious because the Spanish survey boat spent more than 20 hours in British water.

Spain has long maintained that the waters surrounding the peninsula – unlike Gibraltar itself – were never ceded to Britain as part of the 1713 treaty of Utrecht. Madrid therefore feels free to send police and other state vessels into the disputed zone whenever it wants, prompting regular maritime stand-offs with the Royal Gibraltar Police.

The incident marks the latest escalation in tensions between the two countries, which reignited several months ago when the Gibraltar government began placing concrete blocks in the water off the peninsula, which the Spanish view as their own.

In retaliation for what the Spanish government saw as an aggressive act against their fishermen, it instituted heightened border checks on vehicles trying to cross into Spain, which has caused tailbacks of several hours.

The European Commission found last week that those checks were legal under European law, despite British claims to the contrary.

British MPs have reacted angrily to that judgment. On Tuesday, Bob Stewart, a Conservative MP and former army colonel, argued in parliament that Britain should run training exercises for troops in Gibraltar, an action likely to trigger further retaliation from the Spanish.

Gibraltar and British officials worry that, if left unchecked, the near-daily stand-offs in the busy Bay of Algeciras could one day erupt into violent clashes. Britain’s minister for Europe warned on Tuesday that recent manoeuvres by Spain’s Guardia Civil “put lives at risk”.

Get alerts on Gibraltar tensions when a new story is published

Copyright The Financial Times Limited 2018. All rights reserved.

Follow the topics in this article