Britain's ambassador to Spain has formally protested to the Madrid government over "disproportionate" checks at the border with Gibraltar at the weekend, the Foreign Office (FCO) said on Tuesday evening.
Giles Paxman visited Spanish foreign secretary Gonzalo de Benito to lodge his protest and to seek an explanation over comments made by his colleague foreign minister Jose Garcia-Margallo, an FCO spokesman said.
Spain was accused by Gibraltar's chief minister of "sabre-rattling" and behaving like North Korea after Garcia-Margallo announced proposals to levy border crossing fees and other punitive measures against the British territory.
The FCO spokesman said: "Giles Paxman visited the Spanish secretary of state (for foreign affairs) Gonzalo de Benito to formally protest at the disproportionate border checks at the weekend and to seek an explanation of foreign minister Garcia-Margallo's comments that he intends to target Gibraltar with future punitive measures. The ambassador re-iterated that the UK would stand shoulder to shoulder with Gibraltar in face of threats from Spain."
The ambassador's visit came as a former minister urged the UK to reopen negotiations with Spain aimed at sharing Gibraltar's sovereignty. Peter Hain, who led negotiations aimed at resolving the situation while a minister in Tony Blair's government, said a sovereignty deal would end the current difficulties being faced by Gibraltarians in the dispute with their Spanish neighbours.
The Government has insisted there will be no compromise over the sovereignty of Gibraltar, and Foreign Secretary William Hague has vowed to stand "shoulder to shoulder" with its citizens in response to heightened pressure and increasingly belligerent rhetoric from Madrid.
A deal on ending the dispute, which dates back to the Treaty of Utrecht 300 years ago that ceded the territory to Britain, appeared close in 2002 after negotiations between then Europe minister Hain and his Spanish counterpart. Hain told the BBC Radio 4 Today programme this morning that the Spanish got "cold feet" and backed off.
"There was a historic opportunity to have joint sovereignty which would have protected Gibraltarians' way of life - they could remain British citizens, but it also recognised Spain's historic claim at the root of this," he said.
Hain's comments are likely to be met with hostility in Gibraltar, where citizens overwhelmingly rejected the prospect of a shared sovereignty deal in a referendum in 2002.
Relations between Gibraltar and Spain have deteriorated in recent months in a row over fishing grounds, with Spanish ministers raising the prospect of imposing a 50 euro (£43) levy on vehicles crossing the border and the possibility of closing airspace.
Garcia-Margallo said the proceeds of a border fee could be used to help Spanish fishermen who have lost out because of damage to fishing grounds allegedly caused by Gibraltarian authorities following the creation of an artificial reef. Gibraltar's chief minister, Fabian Picardo, likened the comments coming out of Madrid to something from the Franco-era.
The Foreign Secretary offered his support to Picardo and emphasised that the UK "stands shoulder to shoulder with the people of Gibraltar" at a time of "increasing Spanish pressure and rhetoric". Hague said: "I also highlighted that we will respect Gibraltar's 2006 constitution and the commitments the UK has repeatedly made not to compromise on British sovereignty over Gibraltar.
"We discussed the need for a political solution to the current tension with Spain, which would be firmly in the interests of communities on both sides of Gibraltar's border with Spain."
European Commission (EC) spokesman Frederic Vincent confirmed that controls on the Spain-Gibraltar border are allowed because the latter is not included in the Schengen Borders Agreement, which permits people to travel freely within the Schengen area of 26 countries.