The prime minister called EU Commission President Jose Manuel Barroso to raise concerns that the border checks are violating the bloc's rules about free movement. His office said today that Cameron urged Barroso to send an EU monitoring team to the Gibraltar-Spain border to gather evidence.
Spain has long laid claim to Gibraltar -- the massive rock at the western entrance to the Mediterranean Sea -- and the tiny territory is the source of occasional diplomatic friction between Madrid and London.
The UK says it is considering taking Spain to court over the border checks for vehicles entering Gibraltar. Britain reiterated today to Barroso that it feels the checks are politically motivated and disproportionate.
Cameron's office said the prime minister made clear to Barroso that Britain wants to resolve the dispute through dialogue and has been working to "de-escalate" the border issue but despite those efforts, the border checks are continuing.
"We believe that the European Commission, as guardian of the treaties, should investigate the issue," Cameron's office added.