Ministers are guaranteeing Gibraltar that Spain will not be allowed to exclude it from any post-Brexit deal struck with the EU.
The commitment comes amid fears that Madrid is seeking to exploit its leverage over Brexit to reopen the question of the Rock’s sovereignty.
The European Council sparked anger by granting Spain a veto over the territory’s fate after Brexit.
The move raised the prospect of the UK being forced to choose between the Rock and a potential deal with the EU.
Gibraltar’s chief minister Fabian Picardo is in London for talks with ministers over the negotiations today.
There have been fears that Spain is seeking to exploit Brexit to reopen the question of Gibraltar’s (pictured) sovereignty
Mr Picardo said that Gibraltar’s parliament holds its own veto, with the power to decide which parts of the final Brexit agreement will apply to the 30,000 inhabitants of the Mediterranean outpost.
But he said there was no question of reopening discussions on its future status, telling BBC Radio 4’s Today programme: ‘Sovereignty is something which is settled. It was settled in the Helsinki accords and in Utrecht that the sovereignty of Gibraltar belongs to the UK and the people of Gibraltar.
‘We don’t barter with sovereignty today as if we were in the 17th century, with kings passing around sovereignty of pieces of land.
‘What we do is look at the interests of the people. What we do is talk to people and ask them what matters.
‘We are very linked to the UK, we see the world through British eyes and we don’t want to change that.’
Liberal Democrat leader Sir Vince Cable urged the Government to be firmer in its defence of Gibraltar’s links to the UK after Brexit.
Sir Vince told the BBC: ‘It is an issue of fundamental principle. This has been attached to the UK for two centuries.
‘We have seen off repeated demands by Spain to have control over the Rock, which has been a fundamental part of British interests.
Gibraltar’s chief minister Fabian Picardo said its parliament can decide which parts of the final Brexit agreement will apply to the 30,000 inhabitants of the Mediterranean outpost
‘We shouldn’t allow Brexit to be used as a cloak for giving away what is a substantial British commitment. ‘Let’s not forget that all of these people want to remain in the UK just as much as the majority of people in Northern Ireland.’
The EU insists that Spain can stop a transitional deal or future trade relationship applying to Gibraltar unless there is a Spain-UK agreement.
A UK government spokesman said: ‘The EU’s guidelines are a matter for the EU and the other member states.
‘The prime minister has said that as we negotiate these matters we will be negotiating to ensure that the relationships are there for Gibraltar as well.
‘We are not going to exclude Gibraltar from our negotiations for either the implementation period or the future agreement.’