The world can not delay taking action on climate change any longer, Gordon Brown has warned.
Addressing the Major Economies Forum in London, the prime minister said that countries must use the Copenhagen summit in December to secure a new deal on climate change.
"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," he said.
"We can't afford to fail. If we fail, we pay a heavy price. He said. "For the planet, there is no plan B.”
The MEF was set up to give officials from around the world a chance to hammer out differences before Copenhagen.
Failure to act now would result in a climate "catastrophe" the prime minister added.
Brown's speech comes as the environmental charity WWF published a report that warns dangerous climate change was almost inevitable unless the world switched to a low carbon economy by 2014.
Keith Allott, head of climate change at WWF said: "If we wait until later than 2014 to begin aggressively tackling the problem, we will have left it too late to ensure that all the low-carbon solutions required are ready to roll out at the scale needed if we intend to keep within the world's remaining carbon budget.
The Guardian reports that Downing Street is concerned that US presidentBarrack Obama does not have enough political capital to drive throughan agreement, and that he will instead seek a bilateral deal with Chinaon emissions, circumventing the UN process.
Brown told the meeting: "Inevery era there are only one or two moments when nations come togetherand reach agreements that make history, because they change the courseof history. Copenhagen must be such a time. There are now fewer than 50days to set the course of the next 50 years and more."
The Maldives government staged an ocean floor cabinet meeting on Saturday to highlight the threat rapid climate change presents to their nation of low-lying islands.
Around 80 per cent of the country is less than one metre above sea level, and risks being wiped out entirely if sea levels continue to rise.
