Even as the leaders of the European Union gathered to sign a landmark treaty designed to improve the way the 27-nation bloc functions, there were signs that the skepticism and self-interest, which has dogged the 50-year-old organization, would still be a feature of its future.

All of the EU's 27 prime ministers or heads of state and their foreign ministers were in attendance to the sign the 250-page Lisbon Treaty in the Portuguese capital on Thursday -- bar one. British Prime Minister Gordon Brown was absent from the latest show of togetherness, citing "long-standing diary commitments" in London. Foreign Secretary David Miliband signed the treaty for Britain at the ceremony.

While he was expected to sign the treaty later in the day, Brown's failure to sign alongside his EU allies renewed the charges of Euro-skepticism which have followed him for most of his recent career.

Brown's mixed signals over Europe

The treaty is seen as being wildly unpopular in the UK with many believing it cedes too much power to the feared "EU superstate" and critics of the prime minister have already called his delayed signing a "cowardly attempt to distance himself from the EU pact."

"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 Center for European Reform, a London-based think tank, in an interview with AFP. "It's a piece of very ham-fisted diplomacy on the part of Brown."

Brown came under heavy domestic fire earlier this year when he resisted pressure for a referendum on the new treaty despite it being part of the Labour Party's 2005 manifesto, justifying his willingness to be involved by stating that Britain had negotiated opt-outs in key policy areas, meaning its sovereignty remained protected.

His apparent support for the Lisbon Treaty also caused consternation due to his previous vehement resistance to influence from Brussels while finance minister under Tony Blair when he reportedly vetoed Blair's plans to take Britain into the European single currency.

Prime minister's absence hints at future challenges

Even before Thursday's awkward handling of the Lisbon treaty signing, commentators had already noted that Brown has not yet traveled to Brussels, nearly six months after taking office.

The treaty, which seeks to simplify and speed up the EU's decision-making process and give the EU more clout on the international stage, is seen as the EU's chance for reform and an opportunity to put national interests aside in favor of a more common stance.

The signing ceremony, with its grand setting of Lisbon's magnificent Jeronimos Monastery and the background music of Dulce Pontes, one of Portugal's most renowned singers, was also supposed to be a celebration of togetherness. Brown's absence reminded everybody that signing the treaty was just the start. It would be the implementation of the ideals within that would define its success.

The Lisbon Treaty is the first major overhaul of EU rules since the Treaty of Nice was agreed on, almost exactly seven years ago. Under the new treaty, the bloc will create the role of a new EU president, appointed for up to five years, which will replace the current rotation system where member states take turns to hold the EU presidency for six months.

A treaty to empower Europe

It also updates the EU's executive body, the Commission, which draws up EU-level laws and makes sure that they are implemented. At present, every single EU member state nominates a commissioner, but the treaty reduces that number to 18.

"The Treaty of Lisbon will reinforce the Union's capacity to act and the ability to achieve those goals in an effective way," said EU Commission President Jose Manuel Barroso in a speech at the start of the ceremony. "As such, it will help the Union to deliver better results to European citizens.

"It is the treaty of an enlarged Europe from the Mediterranean to the Baltic, from the Atlantic Ocean to the Black Sea. A Europe that shares common values and common ambitions," Barroso said. "For the first time, the countries that were once divided by a totalitarian curtain are now united in support of a common treaty that they had themselves negotiated," Barroso said, in reference to the former Soviet states which have joined during the bloc's expansion.

An historic day

"History will remember this day as a day when new paths of hope were opened to the European ideal," said Portuguese Premier Jose Socrates, whose country currently holds the EU presidency and has played a fundamental role -- along with the German EU presidency in the first half of 2007-- in getting EU leaders to agree on the text during the course of the year.

Socrates was among many leaders who offered their thanks to German Chancellor Angela Merkel, who steered the negotiations which led to the agreed text.

In his speech to the assembled leaders, Germany's Foreign Minister Frank-Walter Steinmeier said that the treaty would ensure that "Europe becomes more transparent, Europe becomes more democratic, and Europe becomes more efficient."

The German president of the European Parliament, Hans-Gert Pöttering, added that the treaty was hugely significant as it showed a bloc willing to work together.

"Remember," he said, "it is our solidarity that unites us."