Prime Minister Gordon Brown has warned of a "catastrophe" for the planet if action to tackle climate change is not agreed at forthcoming UN talks on global warming.
Speaking to representatives of 17 countries at the Major Economies Forum, convened as part of efforts to secure a deal at the UN Summit in Copenhagen in December, he warned of the economic, human and ecological impact of a failure to cut the emissions driving up temperatures.
The costs of failing to address global warming would be greater than the impact of the two world wars and the Great Depression, he said.
He told the forum, gathered in London for the second day of talks, that he believes a deal in Copenhagen is possible.
But with fewer than 50 days to go before the UN talks, he warned them that countries were not making progress quickly enough to reach agreement.
He called on world leaders to work together directly to achieve a deal which sets out binding targets for rich countries to cut their emissions, action by developing nations and finance to help the poorest countries cope with the impact of climate change.
"We can't afford to fail. If we fail, we pay a heavy price," he warned. "For the planet, there is no plan B."
Mr Brown added: "If we do not reach a deal at this time, let us be in no doubt: once the damage from unchecked emissions growth is done, no retrospective global agreement in some future period can undo that choice.
"By then it will be irretrievably too late.
"So we should never allow ourselves to lose sight of the catastrophe we face if present warming trends continue."
