Parliamentarians endorsed the treaty by 525-115 with 29 abstentions. European Commission Vice President Margot Wallstrom told lawmakers that the agreement signed by heads of state and government in the Portuguese capital last December "strengthens Europe's democratic legitimacy".

All 27 EU member states must individually ratify the wide-ranging text for it to come into effect by next year, as scheduled. But only Ireland is constitutionally bound to put it to a plebiscite. The governments of France, Hungary, Malta, Romania and Slovenia have already approved the document on behalf of their citizens.

Euroskeptics accuse the EU leaders of refusing to give citizens a say on a text that is practically identical to the draft European consitution already rejected by French and Dutch voters in referenda in 2005.

The constitution repackaged?

Like the rejected charter, the treaty provides for a longer-term president and a foreign policy envoy, a simpler, more streamlined decision-making system and more say for the national and European parliaments. It does not include such symbols of statehood as a flag or an anthem.

The agreement was painstakingly hammered out over months and includes key policy opt-outs for Britain and Poland from the EU's Charter of Fundamental Rights and judicial co-operation.

"This is nothing less than a massive exercise in deceit," said Nigel Farage of the UK Independence Party. He reminded parliamentarians that former British Prime Minister Tony Blair had promised the British people a referendum on the constitution.

Defence of Parliamentary ratification

Slovenian Secretary of State for European Affairs Janez Lenarcic, whose country holds the rotating presidency, responded: "There is nothing wrong with parliamentary ratification. All EU member states are representative parliamentary democracies."

European Parliament President Hans-Gert Poettering, a German Christian Democrat, said the assembly represented the European people. He told the protesters: "If your parents could see you, they would be ashamed."

Spanish conservative MEP, Inigo Mendez de Vigo, who was one of the authors of a parliamentary report on the Lisbon Treaty, welcomed the agreement. "The treaty is a political solution, a compromise to get us out of the crisis, the impasse. But it also gives the European Union all the instruments to respond to the concerns of the citizens."