Analysts said the green movement's lobbying talent is wasted at such mega-events where their loud protests go largely unheard by government delegations and a change in strategy is needed to wield more clout at future summits.

"The real issue is between governments and public opinion. Public opinion in some countries is obviously not requiring leaders to come here and do the right thing," said Friends of the Earth International Deputy Director Tony Juniper.

"The question is how NGOs (non-governmental organisations) can engage better with the public to the point where the public is saying in a very clear way to the politicians that they have to come to these things and deliver," he added.

Environmentalists slammed the summit's "action plan", saying it lacked targets for the use of renewable energy sources like wind or solar power. They said a pledge to halve the number of people who lack sanitation - a staggering 2.4 billion people - by 2015 was weakly worded and not binding.

"We have not moved forward an inch," said Steve Sawyer of activist group Greenpeace, one of many activists who felt governments and big business had sidelined NGOs at the summit.

As green campaigners withdrew to lick their wounds, some activists said it was time to re-think their approach.

"This is a wake up call for us all," said Liz Hosken, a spokeswoman for NGOs which gathered at a parallel Peoples Earth Summit some 10 km (6.5 miles) away from the main summit venue.

"The NGO community have now learnt that trying to argue about the wording of the text is like trying to stop the Titanic sinking," she added.

NOTABLE PUBLIC SUCCESSES

Tireless self-publicists and expert managers of the media, NGOs have scored some notable successes in the past by bringing the power of public opinion to bear.

Greenpeace led a public campaign in 1995 that forced Royal Dutch/Shell to abandon plans to sink its ageing Brent Spar oil platform at sea, even though independent scientists had said it was the most environmentally friendly option.

And activists' attacks on genetically-modified crops have played a large part in fostering public concern in Europe that the technology is not safe.

The World Bank - a traditional foe of the NGO community - said the activists had a bigger impact than they think.

"They have not got what they wanted by a long way, but without the NGOs shouting as loud as they have done, we might not even have got what we did," said Robert Watson, chief scientist at the World Bank.

Greenpeace Political Director Remi Parmentier said that while business initiatives cannot be a substitute for government action, NGOs must work more closely with other stakeholders to achieve their goals.