"The Kyoto agreement... amounts to effectively a one-percent reduction in emissions, whereas the evidence we have is that we require a 60-percent reduction in emissions by 2050," Blair said.
"The single biggest long-term problem we face is the issue of climate change," he said.
The Kyoto Protocol requires wealthy industrialised countries to make an overall cut of 5.2 percent in emissions of carbon dioxide gases by 2012.
Blair, who was speaking in the House of Commons, Britain's lower legislative chamber, admitted he did not share the United States view on Kyoto. Washington has so far refused to ratify the treaty.
But he said it would be wrong to give up trying to convince Washington to change its mind, underlining that it was not only US President George W. Bush that was opposed to ratifying the treaty, but the US Congress as well.
"I don't think we should give up on dialogue with the US," Blair said.