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Liam Fox said Cameron needed to make clear any suggestion from Spain to push for joint sovereignty was intolerable no matter the result of the referendum. Yesterday Gibraltar's chief minister Fabian Picardo warned Spain could introduce tougher restrictions along the enclave's only border into mainland Europe if Britain left the EU, threatening the territory's access to the single market and free movement. His comments come as Spanish foreign minister José García-Margallo suggested Gibraltarians would be forced to once again consider joint-sovereignty with the Spanish.

It came after Foreign Secretary Philip Hammond infuriated Brexit campaigners earlier this month by claiming a vote to leave the EU would threaten Gibraltar’s security. He said: "I genuinely believe that the threat of leaving the European Union is as big a threat to Gibraltar's future security and Gibraltar's future sovereignty as the more traditional threats that we routinely talk about." The comments came after David Cameron warned Brexit would be the start of World War Three. But today Mr Fox said the suggestion went "way beyond the acceptable limits" of the EU debate.

GETTY Questions have been raised about the future sovereignty of Gibraltar if the UK leaves Europe

He told BBC One’s Andrew Marr Show: "I think the one thing you never do in any campaign is to play with security. "The sovereignty of the people of Gibraltar has always been guaranteed by the United Kingdom. "To pretend in any way, shape or form that that policy would change whether we are in our outside the European Union is inexcusable.

BBC Liam Fox said suggestions Gibraltar could be under threat were "inexcusable"

To pretend in any way, shape or form that that policy would change whether we are in our outside the European Union is inexcusable Liam Fox