Gibraltar's sovereignty is unchanged and "cannot conceivably change" unless consent is given by both Gibraltar and Britain, Boris Johnson has said.

It comes after speculation about The Rock's future following Brexit and even a suggestion the UK might go to war over the issue by former Tory leader Michael Howard.

Mr Johnson said on Monday morning: "I think the position of the Government is very, very clear. Which is that the sovereignty of Gibraltar is unchanged and it's not going to change, and cannot conceivably change without the express support and consent of the people of Gibraltar and the United Kingdom."

Gibraltar's Chief Minister added the territory will not allow itself to become a bargaining chip or a victim in Brexit negotiations.

Fabian Picardo said Spain was "bullying" Gibraltar and that a clause in the EU's joint position on exit talks embroiling the territory in any final agreement should be removed.

"We voted to stay in the European Union so taking it out on us is to allow Spain to behave in the manner of the bully," he said.

Former foreign secretary Jack Straw called the idea of war with Spain over Gibraltar is "absurd" and said it "reeks of 19th century jingoism".

The Labour ex-cabinet minister said Gibraltar was unlikely to be a key facet of Brexit negotiations over the next two years.

He intervened following Mr Howard’s outlandish claim that Theresa May would go to war to protect the territory’s sovereignty, amid increased tension around its status in the wake of the decision to trigger Article 50.

Spain's Foreign Minister Alfonso Dastis said on Monday: "The Spanish government is a little surprised by the tone of comments coming out of Britain, a country known for its composure."