Environment Secretary David Miliband is being urged to take a leadership role when he attends top climate change talks next week in Nairobi.
The call comes from Friends of the Earth, ahead of UN negotiations which aim to shape the future of an international climate agreement.
A 700-page, Treasury-commissioned report by Sir Nicholas Stern on the economics of climate change launched last week suggested that governments can afford to act and must do so urgently to avoid disastrous economic costs.
The report says that measures to tackle climate change will have economic benefits and that an investment of just 1% in the global economy will avoid costs of 10%.
Friends of the Earth international climate campaigner Catherine Pearce said: "The threat is overwhelming. The urgent need for action cannot be ignored. The talks in Nairobi must lead the international community to the tough emission cuts needed - and these must be firmly agreed by 2008.
The momentum we saw in Montreal last year demonstrates the desire for action, but ministers arriving in Nairobi must speed up this process urgently.
"We have a strong international framework already in place. We must build on Kyoto and strengthen it, with all developed countries committing to deeper cuts after 2012 and some of the bigger developing countries also joining the process.
"There must also be a greater commitment to the needs of the most vulnerable countries which are already bearing the brunt of climate change."
