By Alex Kirby
BBC News Online environment correspondent
President Bush's administration has been accused of suppressing and distorting scientific findings that run counter to its own political beliefs.
The president feels the chill wind of scientific scepticism
The charge comes from an American body, the Union of Concerned Scientists, in a statement with more than 60 supporters.
The signatories, who include 12 Nobel Prize winners, say scientific integrity must be restored to policy-making.
The White House called the statement "disappointing" and said decisions were taken on the best available science.
The UCS chairman is Dr Kurt Gottfried, emeritus professor of physics at Cornell University.
He said: "Across a broad range of issues, the administration has undermined the quality of the scientific advisory system and the morale of the government's outstanding scientific personnel.
"Whether the issue is lead paint, clean air or climate change, this behaviour has serious consequences for all Americans."
Dr Gottfried said: "We're not... taking issue with the administration's policies. We're taking issue with the administration's distortion... of the science related to some of its policies."
Russell Train, one of the statement's supporters, headed the Environmental Protection Agency under former Republican Presidents Nixon and Ford.
He said: "Science, to quote President Bush's father, the former president, relies on freedom of inquiry and objectivity.
"But this administration has obstructed that freedom and distorted that objectivity in ways that were unheard of in any previous administration."
Dr Sherwood Rowland, who won a Nobel Prize for his studies of atmospheric ozone, said the consensus of scientific opinion on climate change was being ignored.
Government reports had been censored to remove views out of line with President Bush's policies, he said.
Coral reef reveals climate clues: Altered by the White House?
Dr Rowland said: "The public deserves rational decision-making based on the best scientific advice about what is likely to happen, not what political entities might wish to happen."
Scott McClellan, President Bush's spokesman, said: "I can assure you that this is an administration that makes decisions based on the best available science."
John Marburger, director of the White House Office of Science and Technology Policy, said he found the statement "somewhat disappointing".
He said it made "some sweeping generalisations about policy in this administration that are based on a random selection of incidents and issues".
Professor Marburger said: "I don't think the statement makes the case for the sweeping accusations that it makes."
The UCS website describes the organisation as "an independent non-profit alliance of more than 100,000 concerned citizens and scientists".
Coral reef image courtesy of US National Oceanic and Atmospheric Administration.