A Downing Street spokesperson has said:

"The Prime Minister called the Spanish Prime Minister, Mariano Rajoy, this morning to raise serious concerns about actions by the Spanish at the border with Gibraltar and suggestions from Spanish Foreign Minister Jose Garcia-Margallo that they may introduce further measures.

"The PM made clear that our position on the sovereignty of Gibraltar and its surrounding waters will not change. He also reiterated, as the PM and Mr. Rajoy had previously agreed, that the issue should not damage our bilateral relations. However there was a real risk of this happening unless the situation at the border improved.

"Mr Rajoy agreed that he did not want the issue to become an obstacle in the bilateral relations and that we needed to find a way to de-escalate the issue. As a next step, the Foreign Secretary should speak to Mr. Garcia-Margallo to discuss a way forward.

"In the meantime, Prime Minister Rajoy committed to reducing measures at the border. Both leaders agreed that there should be a solution to the fishing dispute."