Mr Piqué described UK as a friendly country and an ally
Former foreign minister Josep Piqué defended proposals for co-sovereignty of Gibraltar and branded joint rule a “great opportunity to close an obsolete and anachronistic reminiscence of the past”.
As Britain prepares to leave the EU, Mr Piqué stressed the UK "is still a friendly country and an ally in the Atlantic Alliance".
But the former Spanish diplomat took aim at Brexit warning: "We are no longer talking about a friendly agreement between equals, partners, allies and friends.
“We are talking about a state that has decided to leave the European Union and, with that decision, drags along a territory that will be severely affected, unless they agree to be an active part of a solution that is satisfactory for all parties.”
Spain has refused to renounce its claim to the Rock but the territory’s chief Fabian Picardo has repeatedly rejected any Spanish attempt to grab sovereignty.
The territory was ceded to Britain in 1713.
Gibraltar rejected the idea of Britain sharing sovereignty with Spain by 99 percent to 1 percent in a 2002 referendum.
In his new report, titled “Gibraltar: what could have been and what could be”, Mr Piqué says 15 years have passed since the last draft of the “Joint declaration of Hispanic-British Gibraltar", in which the idea of co-sovereignty was first put forward.
He added that at the time, British Foreign Secretary Jack Straw "clearly understood the need and desirability of providing a stable, secure and prosperous future for Gibraltar, and that this was only possible in the medium and long term through an agreement with Spain."
Mr Piqué said in a post-Brexit world, Spain’s EU membership should be seen as a strength, emphasising that its strong position at the negotiating table “must be played with intelligence, discretion, generosity and time control.”
Things you may not know about Gibraltar
Mon, April 3, 2017
Gibraltar is a confusing place, especially if you have never been yourself
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Gibraltar has its own political system that makes many decisions within the territory but issues like defence and foreign affairs are determined by the UK Government in London
A total of 96 per cent of voters in Gibraltar voted for Britain to remain in the EU in the historic June referendum.
Mr Piqué added he believes that the idea of co-sovereignty “remains the best option, in the absence of real alternatives – despite the initial rejection of the Gibraltarians.”
But the former diplomat's comments come as Prime Minister Theresa May stressed Britain will continue to work with the EU to protect the sovereignty of Gibraltar in the newly-released Conservative Party election manifesto.