Meeting for the first time since European elections earlier in June, the heads of state also nominated president Barroso to lead the commission for a second term and agreed to European-level supervision of the financial industry.

The summit touched on economic recovery efforts, preparations for the upcoming international conference on climate change in Copenhagen and illegal immigration.

The EU also renewed calls for the release of Myanmar’s opposition leader Aung San Suu Kyi, who spent her 64th birthday in detention.

Ireland received legally binding assurances that the treaty would not undermine its military neutrality or infringe on its right to set taxes and policy on ethical issues such as abortion – those were the concerns blamed for the treaty’s failure in a referendum last summer. The guarantees were Ireland’s condition for holding a new vote in the autumn.

The Lisbon treaty is designed to streamline European decision-making, which has become more unwieldy since the EU expanded. All 27 member countries must approve the treaty for it to take effect.

Moving swiftly on financial supervision, EU leaders agreed to set up a European system to prevent another global economic crisis. It involves two new bodies: one to watch for system-wide threats to financial stability and the other to ensure financial soundness at the level of individual firms.

The summit also endorsed a commission proposal to fast-track €19 billion in EU funds to stem rising unemployment. The leaders said economic recovery efforts are having an effect but further measures to help the struggling financial sector may be needed.

On climate change, leaders agreed that all countries except the poorest should help finance the fight against global warming in developing countries. The summit called for more efforts to fight illegal immigration, including tighter border control.

President Barroso also briefed leaders on his efforts to avert another disruption in national gas supplies from Russia, saying a crisis could be “weeks, not months” away.