Washington ? President Bush’s administration distorts scientific findings and seeks to manipulate experts’ advice to avoid information that runs counter to its political beliefs, a private organization of scientists asserted on Wednesday.

The Union of Concerned Scientists contended in a report that “the scope and scale of the manipulation, suppression and misrepresentation of science by the Bush administration is unprecedented.”

“We’re not taking issue with administration policies. We’re taking issue with the administration’s distortion … of the science related to some of its policies,” said the group’s president, Kurt Gottfried.

White House spokesman Scott McClellan said he had not seen the report but that the administration “makes decisions based on the best available science.”

White House science adviser John Marburger said he found the report “somewhat disappointing … because it makes some sweeping generalizations about policy in this administration that are based on a random selection of incidents and issues.”

He added, “I don’t think it makes the case for the sweeping accusations that it makes.”

Marburger acknowledged that the complaint was signed by a wide assortment of prominent scientists, including Nobel Prize winners and recipients of the National Medal of Science.

That, he said, is “evidence we are not communicating with them as we should, and I’ll have to deal with that.”

“We need to have a dialogue about what is actually happening, but this report does not do it,” Marburger said.

F. Sherwood Rowland, a Nobel Prize winner for his studies of ozone in the atmosphere, was particularly critical of the administration’s approach to climate change.

He said the consensus of scientific opinion about global warming was being ignored and that government reports had been censored to remove views not in tune with Bush’s politics.

The union’s report came at the same time the National Academy of Science was releasing its own study that commends the administration’s plan to study climate but also expresses concern that the research was underfunded and not pursued vigorously enough.

Asked if they had seen any political interference in the climate program, Thomas E. Graedel of Yale University, chairman of the academy committee, said his group did not look for that. But, he added, he had not seen anything that would suggest the research plan had such political concerns.

A commission member, Anthony L. Janetos, noted that the climate program involves high-level members of the administration.