Britain has made a formal protest to Madrid after Spanish officials opened British diplomatic bags on the border with Gibraltar in a "serious infringement" of the Vienna Convention, the Foreign Office said today.
The incident on November 22 is the latest flare-up between Britain and Spain over the British-held territory in recent months.
A Foreign office spokesman said: "As far as we are concerned there is no justification for this infringement of the UK's rights under the Vienna Convention. Official correspondence and diplomatic bags are inviolable."
Britain responded with a formal diplomatic note of protest yesterday, less than a week after it summoned the Spanish ambassador in London following an incursion into Gibraltar's territorial waters by a Spanish state research vessel.
"The British embassy in Madrid has formally protested to the Spanish Ministry of Foreign Affairs via note verbale and we await an urgent explanation," a Foreign Office spokesman said.
"We will consider further action in light of that explanation."
He said Britain had asked Spanish authorities to investigate what occurred "and take action to ensure it does not happen again".
"This was a serious infringement of the principles of the Vienna Convention on Diplomatic Relations," the spokesman said.
"Protocol concerning official correspondence and the diplomatic bag is governed by the 1961 Vienna Convention on Diplomatic Relations.
"There are long-established and internationally-accepted articles concerning official correspondence and the diplomatic bag to which the Foreign Office adheres.
"We expect other parties to the Convention, including EU and NATO allies, to do the same.
