"British people must and will stand together. We cannot be bullied by Spain. Any agreement must apply equally to the whole British family and that includes Gibraltar. There can be no compromise on this."

In the draft negotiating guidelines for withdrawal talks under Article 50, it states: "After the United Kingdom leaves the union, no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without the agreement between the kingdom of Spain and the United Kingdom."

"The Rock", a British Overseas Territory since 1713 with 30,000 residents, remains a major source of diplomatic tensions.

Gibraltar's chief minister has warned the territory should not be used by Spain as a bargaining chip for Britain’s Brexit negotiations.