LONDON (Reuters) - Gibraltar’s leader on Monday cast EU Council President Donald Tusk as a “cuckolded husband taking it out on the kids” for explicitly proposing that Spain be given a veto over the ties between the British enclave and the European Union after Brexit.

The future of Gibraltar, a British Overseas Territory of just over 2-square miles (6.7 sq km) of rock on Spain’s southern tip, has become the first big dispute of Brexit since Prime Minister Theresa May filed formal divorce papers on March 29.

In the EU’s draft position on the exit talks distributed by Tusk, Gibraltar was given explicit mention. Spain was specifically named as having a veto on the application of any future EU trade deal with Britain.

“Mr Tusk, who has been given to using the analogies of the divorce and divorce petition, is behaving like a cuckolded husband who is taking it out on the children,” Gibraltar’s chief minister, Fabian Picardo, told Reuters in an interview.

“This is clear Spanish bullying.”

Picardo said the EU should remove the reference to Gibraltar, which voted overwhelmingly to stay in the EU, from the draft guidelines.

While years of tortuous negotiations await on issues that could affect trillions of dollars in trade, the Brexit debate in Britain has for three days focused on the future of the “Rock” captured by Britain in 1704 but which Spain wants back.

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The row over Gibraltar illustrates how swiftly the United Kingdom’s influence has declined since the June 23 Brexit vote -- in this case in Spain’s favour -- and how issues perceived by EU powers as marginal can become major complications.

BREXIT ROCK?

After the explicit reference to Spain and Gibraltar became publicly known, May spoke to Picardo and issued a statement saying London was “steadfast” in its commitment to the territory which has positioned itself as a springboard for finance to the EU because of an attractive tax and regulatory regime.

A former leader of May’s Conservative party, Michael Howard, even said she would be prepared to go to war to defend the territory, as then prime minister Margaret Thatcher did with Argentina over the Falkland Islands 35 years ago.

“The Spanish government is a little surprised by the tone of comments coming out of Britain, a country known for its composure,” Spain’s Foreign Minister Alfonso Dastis said during a conference in Madrid.

Ceded to Britain “in perpetuity” in the 1713 Treaty of Utrecht, Gibraltar has long been a bone of contention between London and Madrid and the border was closed for many years during the Franco dictatorship. In a 2002 referendum, Gibralatrians rejected by 98 percent a proposal for joint British-Spanish sovereignty.

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“The sovereignty of Gibraltar is unchanged and is not going to change,” British Foreign Secretary Boris Johnson said on Monday as he arrived for an EU foreign ministers meeting in Luxembourg.

While every EU member state would have a veto over any future trade deal between the EU and post-Brexit Britain, the explicit mention of Gibraltar surprised London and angered the British territory.

May, in her letter to Tusk that triggered Brexit, had not mentioned Gibraltar, which uses the British pound and where Britain operates a military base overlooking the strait.

“The way that the European Council has behaved in allowing Spain to single out Gibraltar in this negative way is really quite pernicious,” Picardo said.

When asked if Gibraltar was now a chip in negotiations, he said: “The last time I looked at this monolithic rock of mine and of the people of Gibraltar it doesn’t look like a chip and its not going on any table.

“We are not going to be a chip and we are not going to be a victim of Brexit as we are not the culprits of Brexit: 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.