President Bush yesterday rejected calls from Britain and the European Union to take a tougher approach on global warming when he renewed his opposition to binding cuts in greenhouse gas emissions.

Speaking at his own climate-change conference in Washington, which European diplomats dismissed as a cynical attempt by the White House to derail UN efforts on a new global-warming accord, Mr Bush called on polluters to cut emissions, but only through voluntary steps.

Before Mr Bush spoke, John Ashton, the special representative on climate change for David Miliband, the Foreign Secretary, expressed Britain’s growing dismay at Washington’s refusal to sign on to mandatory caps on greenhouse gas emissions.

He told The Times that the UN’s effort to forge a new global agreement to succeed the Kyoto Protocol on global warming — which must be done by 2012 — had entered a critical phase. “We cannot do this without binding caps,” Mr Ashton said. “A voluntary approach to greenhouse gases is about as credible as a voluntary approach to speed limits.”

The US is the world’s biggest polluter and European delegates at yesterday’s meeting said that without “real leadership” from the White House in setting binding caps significant progress on tackling global warming will be difficult to achieve.

Connie Hedegaard, the Danish Environment Minister, said: “We need the support of the US, China, India and the other industrialising countries. They will not do anything unless the US is moving.”

The two-day Washington conference was attended by more than 20 of the biggest polluters, including Britain, the EU, China, India and Russia. Mr Bush called on them to come together to set a goal for reducing greenhouse-gas emissions, but, he added, “while keeping our economies growing”.

Mr Bush, who made no attempt to ratify the Kyoto treaty, believes that binding caps will harm the US economy. He said: “Each nation must decide for itself the right mix of tools and technology to achieve results that are measurable and environmentally effective.”

European officials say that the focus of their efforts to change US policy are now on persuading individual US states to follow the lead of California and to look beyond the Bush Administration.

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