The documents, which emerged as Tony Blair visited the White House for discussions on climate change before next month's G8 meeting, reinforce widely-held suspicions of how close the company is to the administration and its role in helping to formulate US policy.

In briefing papers given before meetings to the US under-secretary of state, Paula Dobriansky, between 2001 and 2004, the administration is found thanking Exxon executives for the company's "active involvement" in helping to determine climate change policy, and also seeking its advice on what climate change policies the company might find acceptable.

Other papers suggest that Ms Dobriansky should sound out Exxon executives and other anti-Kyoto business groups on potential alternatives to Kyoto.

Until now Exxon has publicly maintained that it had no involvement in the US government's rejection of Kyoto. But the documents, obtained by Greenpeace under US freedom of information legislation, suggest this is not the case.

"Potus [president of the United States] rejected Kyoto in part based on input from you [the Global Climate Coalition]," says one briefing note before Ms Dobriansky's meeting with the GCC, the main anti-Kyoto US industry group, which was dominated by Exxon.

The papers further state that the White House considered Exxon "among the companies most actively and prominently opposed to binding approaches [like Kyoto] to cut greenhouse gas emissions".

But in evidence to the UK House of Lords science and technology committee in 2003, Exxon's head of public affairs, Nick Thomas, said: "I think we can say categorically we have not campaigned with the United States government or any other government to take any sort of position over Kyoto."

Exxon, officially the US's most valuable company valued at $379bn (£206bn) earlier this year, is seen in the papers to share the White House's unwavering scepticism of international efforts to address climate change.

The documents, which reflect unanimity between the company and the US administration on the need for more global warming science and the unacceptable costs of Kyoto, state that Exxon believes that joining Kyoto "would be unjustifiably drastic and premature".

This line has been taken consistently by President Bush, and was expected to be continued in yesterday's talks with Tony Blair who has said that climate change is "the most pressing issue facing mankind".

"President Bush tells Mr Blair he's concerned about climate change, but these documents reveal the alarming truth, that policy in this White House is being written by the world's most powerful oil company. This administration's climate policy is a menace to humanity," said Stephen Tindale, Greenpeace's executive director in London last night.

"The prime minister needs to tell Mr Bush he's calling in some favours. Only by securing mandatory cuts in US emissions can Blair live up to his rhetoric," said Mr Tindale.

In other meetings documented in the papers, Ms Dobriansky meets Don Pearlman, an international anti-Kyoto lobbyist who has been a paid adviser to the Saudi and Kuwaiti governments, both of which have followed the US line against Kyoto.

The purpose of the meeting with Mr Pearlman, who also represents the secretive anti-Kyoto Climate Council, which the administration says "works against most US government efforts to address climate change", is said to be to "solicit [his] views as part of our dialogue with friends and allies".

ExxonMobil, which was yesterday contacted by the Guardian in the US but did not return calls, is spending millions of pounds on an advertising campaign aimed at influencing politicians, opinion formers and business leaders in the UK and other pro-Kyoto countries in the weeks before the G8 meeting at Gleneagles.