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Leading climate change sceptic Chris de Freitas has lent his name to an American anti-global warming lobby group that has received more than US$2 million ($2.97 million) in funding from ExxonMobil.

The associate professor at Auckland's School of Geography and Environmental Science has lined up with seven American global warming sceptics in a United States Supreme Court case arguing against the regulation of greenhouse gas emissions. It is being hailed as one of the most important environmental cases in decades.

The sceptics' submission is presented by legal counsel for the Competitive Enterprise Institute, a Washington-based conservative think tank "dedicated to advancing the principles of free enterprise and limited government".

Asked whether the submission compromised his independence in climate-change research, Professor de Freitas said he had not received any funding nor was he paid by ExxonMobil. "Yes, the CEI is a lobby agency but its website is just posting the legal submission. The submission itself has nothing to do with CEI as far as I am aware."

Greenpeace campaign manager Cindy Baxter said the CEI was clearly involved in presenting the submission to the court. "The CEI has been paid US$2 million from Exxon."

Professor De Freitas said attacking scientists who promoted scepticism as agents funded by the fossil-fuel industry showed how easily the truth could be distorted.

"I stay away from anything that would tarnish my reputation like money from any industry because, as soon as you start using resources from any particular group, you are seen as untrustworthy."

The CEI is behind the "Carbon dioxide: They call it pollution; we call it life" ad campaign which aired in the US in May. It also co-ordinates the "Cooler Heads Coalition" set up to oppose Kyoto and, says website, has been the beneficiary since 1998 of a total of US$2,005,000 in ExxonMobil research funding.

Last month, US senators John Rockefeller IV and Olympia Snowe called on the world's largest oil company to stop funding climate change denial campaigns, saying ExxonMobil's extensive funding of an "echo chamber" of non-peer reviewed pseudo-science had succeeded in raising questions about the legitimate scientific community's almost universal findings on the detrimental effects of global warming.

Professor de Freitas said using such logic could only mean that all funding contaminated all results.