LONDON (Reuters (LSE: TRIL.L - news) ) - Prime Minister Gordon Brown has warned the G8 against a retreat into isolationism, saying the looming threat to the global economy instead required a speeding up of the fight against climate change and poverty.

In an interview with the Guardian newspaper published on Saturday ahead of a G8 summit in Japan, Brown stressed the need for united action in the West to reduce dependency on fossil fuels and boost food production in developing countries.

His comments came amid fears that the credit crunch would cause the G8 industrialised nations to backpedal on pledges to cut carbon emissions and increase aid to poor countries by $50 billion (25 billion pounds) a year, the Guardian said.

"The world is suffering a triple challenge: of higher fuel prices, higher food prices and a credit crunch," Brown said.

"My message to the G8 will be that instead of sidelining climate change and the development agenda, the present economic crisis means that instead of relaxing our efforts we have got to accelerate them.

"This agenda is not just the key to the environment and reducing poverty, but the key to our economic future as well," Brown said.

He said the summit would be judged on whether it rolled back protectionism, supported cleaner energy, and came up with ways to reduce oil and food prices.

He said he would consider it to be a success if the G8 showed unity, gave strong backing to a new global free-trade deal and pushed ahead on climate change and development.

Brown said he hoped the G8 would make progress towards a new climate change deal next year, agree to "turn the World Bank into an energy bank as well as a development bank", and show a "clear understanding of the importance of renewables to our energy and environmental future".

Britain believed that lack of progress on Africa in 2008 would make it impossible for the United Nations to hit its millennium development goals, set for 2015, but Brown said fighting poverty was in the best interests of the West.

"Unless we help poor countries to become more prosperous through education, health and economic development, we will be piling up the problems of global inequality," he said.

(Editing by Giles Elgood and Alex Richardson).