An anti-corruption watchdog on Thursday warned business leaders at a United Nations summit to urgently tackle corruption costing the global economy some 2.5 trillion dollars (1.8 trillion euros) to help lift millions out of poverty.

Huguette Labelle, chairwoman of Transparency International and board member of the UN Global Compact, said the amount that the World Bank estimated was lost by corruption would be "quite enough to help us remove those that are at the edge of survival around the world to a much different level."

More than 600 senior executives are attending a two-day meeting, which began Thursday, of the Global Compact, a seven-year-old partnership between the UN and companies set up by the previous UN chief, Kofi Annan.

The core concerns of the Compact, such as corruption, transparency and corporate and social responsibility, are "matters of life and death for today and tomorrow," Labelle said at a press conference.

The Compact "provides the stimulus for businesses to act with social responsibility, with environmental sustainability, and with transparency and integrity," she added.

UN Secretary General Ban Ki-moon stressed the same point and urged the 4,000-odd businesses who have signed up to the Compact to implement its 10 principles at all levels of their operations.

"While significant strides are being made we must not be complacent.... Companies need to deepen their integration of the Global Compact principles, especially with respect to subsidiaries and supply chains," Ban said.

Apart from anti-corruption measures, the Compact's 10 principles cover labour relations, human rights and the environment.

The UN's first ever survey on the Compact published this week revealed major shortcomings in a sample of about 400 participants, especially in human rights and anticorruption, despite overall progress.

At least one of the companies

with participants registered for the meeting, electric engineering giant Siemens, is embroiled in corruption investigations in Germany, including allegations of setting up a slush-fund to obtain foreign contracts.

French Foreign Minister Bernard Kouchner, addressing the opening session of the Compact, said there were limits to what it can achieve given its voluntary nature and hinted that legally-binding resolutions might be necessary.

"Given that countries are increasing the number of constraints in the aim of making environmental responsibility a legal imperative, can corporate and social responsibility be limited to a self-defined code of good conduct?" he asked.

Compact director Georg Kell acknowledged this voluntary aspect limited its capacity to influence corporate behaviour.

"The Compact is only a complementary tool, it can never substitute for effective regulation at country level, that goes without saying," he said.