The UK is set to miss a key target on cutting greenhouse gases, Tony Blair has admitted.
Fossil fuel burning is one of the biggest sources of CO2 emissions
The prime minister said the UK was not expected to meet its pledge to cut carbon dioxide emissions to 20% below 1990 levels by 2010.
But he stressed it was on course to hit the 12.5% cut demanded in the Kyoto Protocol on greenhouse gases.
Friends of the Earth says emissions are currently down about 7% - the same as in 1997 when Labour came to power.
The 20% target is a self-imposed goal for the government, which started consultation on five-year climate change plans.
Ministers say the UK has done better than the milder goal set in the Kyoto Protocol, the international agreement to cut six greenhouse gases.
The UK target is 12.5% below the 1990 emissions levels and they are already down 14% overall.
Last December, the European Commission said only the UK and Sweden were on course with existing policies to meet their share of EU targets.
The prime minister says he wants climate change to be a key priority during the UK's presidencies of the G8 and EU in 2005.
BBC environment correspondent Richard Black said the admission the 20% target would be missed was a "very great embarrassment".
Mr Blair was tackled in the Commons by Liberal Democrat leader Charles Kennedy, who asked: "Is it not just again the case, as with so many other things, the prime minister talks a very good game, persuades himself and fails to deliver?"
But Mr Blair said the UK should be proud it was beating the Kyoto target.
"We set a target of 20%; we are on track to get to 14%. We have years to go before we have to meet that target; we do not accept we won't meet it; we've got to make sure we take the measures to meet it."
Making energy suppliers use more renewable sources and encouraging energy efficiency innovation were among plans to achieve more, he said.
Environment Secretary Margaret Beckett said the UK wanted to use its EU presidency to bring aviation into the effort against climate change.
Government chief scientific adviser Sir David King said carbon dioxide emissions had risen since 2002, partly because utilities companies had switched from gas to greater use of coal.
He told MPs it was "crucial" to the UK's credibility for leadership on climate change that it met its domestic goals.
But he argued it was important to focus on the long-term impact of financial incentives. He would have been "absolutely amazed" if some of the current government measures had already begun to "bite".
Sir David said more measures would become acceptable as people realised the consequences of failing to stem global warming.
Not every extreme weather condition could be blamed on the problem, he said. But 30,000 people had died in the summer 2003, the hottest since the 15th Century.
Half of the severity of that summer had been down to climate change and such heats could be the norm by 2045, he warned.
He also suggested the government's target of cutting emissions by 60% by 2050 might not be ambitious enough and could have to be raised to 80%.
'Time running out'
Green Party principal speaker Caroline Lucas MEP said Labour's failure to meet its own targets was an "appalling breach of trust".
"The government knows what to do to reduce emissions, and yet it's doing exactly the opposite," she said.
"This isn't an accident - it's another example of this government making the right noises and then adopting policies that undermine them, sniggering at the gullibility of the British public as it does so."
Conservative spokesman Tim Yeo said Labour was "all talk" on greenhouse emissions.
He said incentives were needed for greener vehicles and more fuel-efficient homes, as well as more work on developing marine power and bio-fuels.
FoE director Tony Juniper has urged Mr Blair to keep to the 20% pledge.
"The UK climate change programme is the last chance for the government to demonstrate it is serious about taking a lead on tackling climate change," he said.
The Confederation of British Industry said too many environmental campaigners blamed business, which had in fact done more than anybody to counter the problem.