According to Jonathan Porritt -- who co-founded the Green Party in Britain -- the green movement is "too narrow, too technical, too depressing, often too dowdy".

Pressure groups must also shoulder some of the blame for the failure to make inroads into tackling issues such as climate change because of their overly negative approach, The Observer newspaper quoted him as saying.

Porritt, who is now an adviser on sustainable development to British Prime Minister Tony Blair's government, makes the comments in his new book, "Capitalism: As if the World Matters", seen by The Observer and to be published this week.

The book argues that all sides should embrace capitalism as "the only economic game in town" and thus search for ways in making free markets work for a more sustainable future, the newspaper said.

Without change by environmentalists, "a continuing decline in (their) influence seems the most likely outcome", Porritt says in his book.

In an interview with The Observer, Porritt added: "Environmental organisations for many years (were) saying 'no' and protecting and stopping because in a way that became part of the culture of the movement.

"There's still a lot of criticising and blame-laying and not enough saying what solutions are available."

Instead, he argued, the movement must emphasise the positive, worldwide benefits of issues such as using clean energy to help tackle climate change.

"If you consider the way the environmental movement portrays climate change, it's the end of the world as we know it," Porritt told the paper.

"In reality, climate change could provide a stimulus to an extraordinary shift in the economy (and) it could improve people's quality of life. You never hear of all that," Porritt told the paper.

Porritt -- a former director of Friends of the Earth who currently advises Britain's heir to the throne Prince Charles -- conceded he had been guilty of negative campaigning in the past.

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