The Spanish government has said it will not back down over the stringent controls at its border with Gibraltar despite Downing Street condemning the move.

The UK government is considering “unprecedented” legal action against Spain over the border controls, which have caused hours of delays for tourists and locals.

A spokesman for David Cameron said on Monday that the border checks imposed in retaliation over Gibraltar’s creation of an artificial reef in its waters, were “politically motivated and totally disproportionate,” reported the Telegraph.

The diplomatic row deepened as British warships set sail for the Mediterranean for a “routine” naval exercise that will see them dock in Gibraltar within the week.

A Spain foreign ministry spokesman said the checks would remain in place. “We insist that they are legal, proportionate and we are obliged to carry them out under the Schengen agreement.”

The Prime Minister was said to be “disappointed” by Spain’s failure to remove the checks.

Cameron had hoped for a “de-escalation” of tension after what he said were productive talks with Spain’s Prime Minister Mariano Rajoy last week.

“The Prime Minister is disappointed by the failure of the Spanish to remove the additional border checks this weekend and we are now considering what legal action is open to us,” Cameron’s spokesman told the Telegraph.

“This would be an unprecedented step so we want to consider it carefully before making a decision to pursue.”

Officials believe the action by Spain contravenes European law and they could now ask the European Commission to investigate the border delays.