Prime Minister Gordon Brown wants Britain to lead the fight against global warming and has hinted that climate change policies must become more ambitious.

Mr Brown makes his first major speech on the issue later and will underscore the need to act immediately to combat global warming and argue that green measures do not have to damage economic growth.

His speech follows a major scientific report from the United Nations which warned that the Earth is heating up at a quickening pace because of human activity and the results could be catastrophic if action is not taken.

The UN's Intergovernmental Panel on Climate Change (IPCC) warned that current trends would see temperatures rise by up to 4C and sea levels 60 cm higher by 2100.

Mr Brown has said he is determined to act and, despite recent reports that he has been under pressure from ministers to curb commitments to reducing carbon emissions, is expected to stress he is looking at the possibility of making them even tougher.

Mr Brown will also cite International

19 November 2007