Tony Blair has attempted to rebuild his reputation among environmentalists in a speech which promised new money and outlined his New Green vision.

Speaking on Tuesday the prime minister unveiled a £100 million fund to develop wind, solar and wave power.

He told his audience at the World Wildlife Fund in London: "This investment in renewable technology is a down payment on our future, and will help open up huge commercial opportunities for Britain."

He also called for a "step change" in the way politicians are dealing with climate change and said rising temperatures were a major global problem.

Blair told the audience that a rising birth rate was the biggest problem facing world leaders. "When my parents were growing up the world's population was under three billion. During my children's lifetime, it is likely to exceed nine billion. You don't have to be an expert to realise that sustainable development is gong to be the greatest challenge we face this century," he said.

He signalled pressure would be placed on the American government to resolve the current impasse on Kyoto commitments. "I hope that by the time we meet in South Africa for the Rio +10 conference next year, Kyoto will have been ratified. We should use Rio +10 to take forward the climate change and sustainable development agendas."

Blair said his aim was to establish Britain at the forefront of environmental change. "I want Britain to be a leading player in this coming green industrial revolution. We have many strengths to draw on. Some of the best marine renewable resources in the world - offshore wind, wave energy and tidal power. And we are leading the thinking in Europe on how to remove the regulatory barriers to development of renewables," he said.

He made a call for global free trade aimed at helping Third World countries saying: "It really is hypocrisy for us, the wealthy countries, to talk about concern to alleviate the poverty of the developing world whilst we block access to our markets."

The prime minister said his commitments would not bring immediate benefits.

"There will always be dilemmas in the politics of environment. Though long-term I have no doubt there are only winners from sustainable development; short-term there is often pain," he said.