Brown will tell this week's meetings of the International Monetary Fund and World Bank in Washington that urgent action is needed and with a level of funding that would make a difference to global emissions.

"The developed world has a responsibility to help developing economies meet their energy needs in an environmentally sustainable way," said Brown, who is expected to succeed Prime Minister Tony Blair before the next election expected in 2009.

"I will propose a World Bank facility - a US$20 billion fund - for developing economies to invest in alternative sources of energy and greater energy efficiency."

Brown's proposal may also help his ruling Labour party regain the initiative on environmental issues ahead of local elections on May 4 after the government admitted it will not meet its key target to cut carbon emissions.

Opposition Conservative Party leader David Cameron, meanwhile, is set to travel to northern Norway this week to see first-hand polar ice caps disappearing because of global warming.

British Treasury officials said countries such as China, India, and Brazil are experiencing rapid growth and a corresponding reduction in overall poverty and are now making investments to meet their increased demand for energy.

Their decisions now will influence their carbon emissions over the next 50 to 100 years and so acting now to channel their investment into more efficient or renewable forms of energy generation can lock in less pollution for the long-term.

At the same time, officials said that the world's poorest countries are the most at risk from the effects of climate change such as droughts and floods and there is an urgent need to support them in improving their capacity to respond.

"Climate change is an issue of justice as much as economic development. It is a problem caused by the industrialised countries, whose effects will disproportionately fall on developing countries," said Brown. who also chairs the IMF's main policy steering group.