Heads of state and government officially signed a new treaty yesterday aimed at simplifying decision-making in the EU and extending its competences to new areas such as energy and judicial co-operation. But the delayed arrival of UK Prime Minister Gordon Brown overshadowed the ceremony.

The official signing ceremony, held in a Gothic church in the Portuguese capital on Thursday (13 December), was overshadowed by the absence of UK Prime Minister Gordon Brown.

Faced with intense pressure from Eurosceptics to hold a referendum on the new text, the British leader only arrived to join his colleagues for lunch and eventually signed the document later, away from the cameras. Brown cited a diary clash for his delayed arrival, with a Parliamentary committee holding him in London.

"There is no better manifestation of his lack of interest in Europe than his thinking that missing the signature would not be a big deal," said Hugo Brady of the Centre for European Reform, cited by AFP.

EU leaders were however quick to turn the attention to the EU's future challenges. "The Treaty of Lisbon will reinforce the Union's capacity to act and the ability to achieve our goals in an effective way. As such, it will help the Union to deliver better results to European citizens," Commission President José Manuel Barroso said at the official ceremony.

According to Sebastian Kurpas, research fellow at the Centre for European Policy Studies (CEPS), the Lisbon Treaty is indeed "likely to make the EU more democratic" through an increased use of legislative procedures that give the European Parliament a greater say, but also the strengthening of national parliaments' role. Kurpas says that it could in principle also make the EU more efficient by streamlining its decision-making.

But the analyst warns that it "will not make the EU more transparent". A number of opt-outs, protocols, declarations and provisions for "flexible integration" make the text largely unreadable for the average citizen, Kurpas says.

Other challenges remain. In order to come into force by the target date of 1 January 2009, the document now needs to be swiftly ratified by member states. So far, Ireland is the only country that is bound by its constitution to hold a referendum, while the other countries are set to ratify the Treaty through their national parliaments.

According to Kurpas, the "stripping of all symbolic elements" from the Treaty will make ratification easier by avoiding the sensitive issue of referenda, but is "likely to entail a price for future integration".