Tony Blair has been lobbying for George Bush's support for a new international treaty on global warming.

On Thursday the Times reported that Downing Street had confirmed the prime minister had held "lengthy discussions" with the American president about a new initiative.

The deal would involve scientific agreement on the scale of the threat and an international programme to develop the technology needed for renewable energy.

The prime minister held talks in Number 10 last week with John McCain, the influential Republican senator, over how to broker an agreement.

President Bush has so far refused to acknowledge the existence of global warming and pulled the US out of the Kyoto treaty on climate change.

But Blair has pledged to make the issue one of two key priorities for Britain's G8 presidency next year.

Ministers have admitted they are set to miss targets set out in successive Labour manifestos for cutting greenhouse gas emissions by 20 per cent.

However Blair told MPs that the government has already achieved its Kyoto commitment of a 12.5 per cent cut.