In a declaration of war over the issue, Greenpeace expressed doubts about the Prime Minister's sincerity over tackling climate change, adding that his record on tackling carbon emissions was "pathetic".

The attack by Stephen Tindale, the Labour-supporting head of Greenpeace, came as Mr Blair and Jacques Chirac, the French President, said that climate change would be "one of the two priorities" for the G8 group of leading industrialised nations when Britain assumed the presidency next year.

But the attack on Mr Blair's record on the issue by Britain's most powerful green lobby group will be extremely damaging to the Prime Minister, who has made tackling global warming a key theme of his tenure in office.

Leading environmentalists joined forces yesterday to criticise Mr Blair's record, accusing him of spin while failing to support measures to reduce carbon emissions from cars, planes. They also accused him of not doing enough to promote energy efficiency measures in the building of new homes.

Mr Tindale, a former government special adviser on the environment who played a key role in framing Labour's policy on climate change, said Mr Blair "cannot be trusted to resist industry lobbying" from car manufacturers and airlines.

"On the climate change issues we have been very supportive of the Government. We have been essentially trying to work with them to promote renewable energy. But we have basically taken a conscious decision that he [Tony Blair] can no longer be given the benefit of the doubt," he said. "So far Blair's record on climate change is almost entirely a record of fine words and no action. His repeated failures on this issue is undermining his diplomatic efforts."

Greenpeace's change of policy follows a series of meetings within the organisation which one figure said amounted to "a declaration of war". The decision to criticise Mr Blair openly over climate change follows the Government's attempts to block energy-efficiency targets in social housing which would help prevent global warming and save lives, and to dilute emissions trading targets.

It also follows Downing Street's decision to "allow industry to emit as much carbon in future as it has in the past".

Mr Tindale, Greenpeace's executive director, said Mr Blair's reheated "tub-thumping speeches" on the world stage were undermined by his "failed" record in Britain.

"Emissions of carbon dioxide have actually increased since Blair became Prime Minister. So much for leadership. Through all this, Blair kept on giving the speeches and we kept on trying to believe him perhaps for too long. We are now going to mobilise a lot more public pressure against them."

He said the Prime Minister's "rhetoric" on wanting to tackle climate change bore no relation to his record. World leaders would "laugh at Tony Blair" because of his dismal record on reducing carbon emissions at home, Mr Tindale said. "They have completely failed on road transport and failed to control emissions from air transport. They are in complete denial."

Carbon emissions have been increasing and experts have warned Britain will not meet its target of reducing them by 20 per cent below 1990 levels by 2010. There are also fears that the Government may try to water down the target in the next few weeks when it publishes its "review" of its policy.

Tony Juniper, executive director of Friends of the Earth, said there was a gaping "gap" between the Prime Minister's rhetoric and leadership on the world stage and his record in the UK. "The leadership position of this country is jeopardised by the position at home," he said. "The credibility of this country on climate change is essentially derived from the policy choices taken by the Conservatives in the 1980s when they decided to shift from coal to gas generation."

Charles Secrett, the former head of Friends of the Earth who now heads Act, a sustainable development campaign group, yesterday said Mr Blair was "all talk and no action".

"Blair thinks he can get away with boosting his green credentials by making a big speech every year on climate change. It's always about the grand scenario and when it comes to putting him own house in order it is always business as usual."

Britain's environmental leaders called on Mr Blair to introduce a crackdown on car and plane emissions and the introduction of tax incentives to go green, when he publishes his climate change review. "We need to shift away from road building and encouraging car use. We need to bring in fiscal incentives to switch away from coal to renewable energy," said Mr Juniper.

Mr Tindale, a former adviser to Michael Meacher, a former Environment minister, said Mr Blair "cannot be trusted to stand up to the motoring lobby, the airlines or even the Treasury". He added: "Fancy speeches are not enough - tackling climate change requires radical action. All the evidence suggests that Blair will not provide it."