David Cameron will visit Gibraltar today to campaign for a Remain vote in the EU referendum, in what will be the first visit by a UK Prime Minister to the Rock since 1968.
The surprise visit was announced late on Wednesday but provoked a swift reaction from the Spanish government.
The government issued an official communique over the visit expressing its displeasure, while the acting Prime Minister warned that Gibraltar was rightfully Spanish whatever the outcome of the EU referendum.
Speaking on the radio, Mariano Rajoy said: "The government does not like the fact that Mr Cameron is travelling to Gibraltar. The debate is about whether the UK remains within the EU or not. It should therefore happen in the UK and not Gibraltar".
Rajoy added: “Spain continues to think that Gibraltar is part of its own national territory, whether Brexit wins or loses.”
Meanwhile José Manuel García Margallo, Spain's acting foreign minister told reporters on Thursday that Brexit would “cause a huge problem for Gibraltar that could be solved by a joint sovereignty agreement.
“We want Britain to remain within the EU but in the case of a Brexit, the situation in Gibraltar would be radically changed.”
“It would be a problem of the first order for The Rock. We would talk to the UK about it and I think the most sensible solution would be to reach an agreement on joint sovereignty.”
Cameron will address a rally at 5.30pm in Casemates Square on the tiny British Overseas Territory home to 32,000 people.
Fabian Picardo, Gibraltar's Chief Minister urged all Gibraltarians to turn out for “the big one”.
“OK, So this is the big one. The one we all thought would never happen has become a reality. The Prime Minister was on a TV screen wishing us a happy National Day at Casements a couple of years ago. Many said to me “pity he won't come in person”. Well the Gibraltar Stronger In Campaign has managed to bring him over.
OK. So this is the big one. The one we all thought would never happen and has become a reality. The Prime... https://t.co/mEWTrkHBg4— Fabian Picardo (@FabianPicardo) June 15, 2016
“That is historic. Never before has a PM come to Gibraltar, in mid-campaign or otherwise, to make an argument before and to make clear the UK's position on Gibraltar”.
“Let's show the world how Gibraltar welcomes its friends! And let's support the Gibraltar Stronger In Campaign so that tomorrow anyone in the UK watching the news will see how much voting to REMAIN in the EU matters to us.”
The latest opinion polls have shown majority support for Brexit, a move that could have dire consequences for Gibraltar.
Earlier this year, Spain's acting foreign minister said that if Britain left the EU he would “raise the question of Gibraltar” the very next day.
“It is safer and more secure for Gibraltar to remain in the EU in order to deny Mr Margallo the opportunity to pounce on us,” Picardo responded.
But Cameron will be preaching to converted as a recent poll showed 88 percent of voters on The Rock would vote to Remain.