Alfonso Dastis, Spain's foreign minister, said he was "surprised" by Britain's response after the EU’s draft Brexit negotiating guidelines appeared to hand Spain an ­effective veto over whether an eventual deal will apply to Gibraltar.

He said: "The Spanish government is a little surprised by the tone of comments coming out of Britain, a country known for its composure."

Mr Picardo said: "Gibraltar is not a bargaining chip in these negotiations. Gibraltar belongs to the Gibraltarians and we want to stay British."