The UK has objected to Argentine congress decision that public transportation should carry signs expressing the country's claim over the Falkland Islands. A law passed by the Argentine Congress says vehicles must declare Las Malvinas son Argentinas, or the Malvinas are Argentine.
The members of congress behind the initiative said it would reflect our undeniable sovereignty over the islands.
The UK Foreign Office said the move was regrettable but not surprising.
The new measure was introduced as part of a wider raft of public transport reforms which were passed unanimously on Thursday.
Senator Teresa Luna, the member of Congress who proposed the new regulation, wrote to the president of the parliament to say: It is directed not only at the foreigner who comes here as a tourist or visits our country, but also at the citizens in general, and will serve to reinforce our history, our culture and our identity.
Argentina lays claim to the Islands, but Britain maintains that it has sovereignty and has accused Argentina of ignoring the wishes of the Island's residents who wish to remain as a British Overseas Territory.
Last year, Falkland Islanders took part in a referendum, voting by 1,513 to three to remain a British overseas territory.
UK Prime Minister David Cameron said at the time that the result could not have sent a clearer message but Argentine President Cristina Fernandez has maintained that the islanders' wishes are not relevant, and has described them as 'squatters'.
The Foreign Office in London condemned the move as a hostile course of action.
But no sign can change the rights of the Falkland Islanders to their own identity and we are determined to uphold that right, the spokesman added.