he move is highly symbolic in Britain as it formally scraps the "European Community", the organisation that Britons originally voted to join in the country's only referendum on Europe 34 years ago.
Mark Francois, Conservative spokesman on Europe, said that the deal showed why the British should have been given a referendum on the Lisbon Treaty.
"As we have long warned, the Lisbon Treaty increases the EU's power at the expense of the countries of Europe," he said. "The new power a single legal personality would give the EU is a classic example.
"It illustrates why it is wrong for Labour to try to deny the British people any say on this Treaty at all."
The decision, taken shortly before Ireland's referendum last week, will mean a new European diplomatic service with over 160 "EU representations" and ambassadors across the world.
Lorraine Mullally, the director of Open Europe, described the move as "a huge transfer of power which makes the EU look more like a country than an international agreement".
"Giving the EU legal personality means that the EU, rather than member states, will be able to sign all kinds of international agreements – on foreign policy, defence, crime and judicial issues – for the first time," she said.
She pointed out that the 1975 referendum was on joining the EC and that it is the European Communities Act that gives Brussels legislation primacy over British law.
"British voters agreed to join the European Communities, not a political union with legal personality with the power to sign all kinds of international agreements," said Miss Mullally. "No one under the age of 52 has ever had a say on this important evolution and it's about time we did."
A restricted document circulated by the Netherlands, Belgium and Luxembourg, seen by The Daily Telegraph, spells out the need for legal changes to set up a European External Service (EEAS), an EU diplomatic and foreign service with "global geographical scope".