The administration has been at loggerheads with scientists since it came to power in 2001 on issues ranging from stem cell research to global warming and the theory of evolution.
It stood accused again of putting ideology over science this week after the administration's former surgeon general charged that it deliberately quashed or downplayed several important health reports for political reasons.
Dr Richard Carmona, a Bush appointee who held the post as the country's chief health educator from 2002 to 2006, told a Congressional committee Tuesday that he was not authorized to discuss certain sensitive subjects in public.
They included embryonic stem-cell research, whose federal funding Bush restricted in 2001, the controversial morning-after pill and sex education.
Carmona admitted to lawmakers that when he had taken up his post he had been "still quite politically naive" but he was "astounded" by the "partisanship and political manipulation" he witnessed.
Health department spokesman Bill Hall rejected Carmona's accusations, saying: "It has always been this administration's position that public health policy should be rooted in sound science."
Michael Halpern, a member of the influential Union of Concerned Scientists, an advocacy group, said scientists believe the Bush administration is the "worst" ever in terms of political interference and censure.
"Information inconvenient to the administration's priorities is sidelined," Halpern told AFP.
In 2004, the Union of Concerned Scientists organized a petition signed by more than 12,000 scientists, including 50 Nobel prize winners and former senior science advisers to several US presidents, to denounce political interference by the Bush administration.
"Scientists believe that political interference is unacceptable," the petition said.
"If our policy makers are going to make fully informed decisions about our health, safety, and environment, they need access to independent science," it said. "Reforms can and should be put in place to insulate science from politics."
The petition has apparently had little impact on the White House.In 2006, NASA's top climate expert, James Hansen, accused the administration in a New York Times interview of pressuring him to censure his research on global warming, notably during the 2004 presidential campaign.
His charges were confirmed by other staffers at the National Aeronautics and Space Administration, leading Democrats as well as Bush's own Republicans in Congress to call for greater scientific transparency in the agency.
A NASA press official, George Deutsch, who was close to Bush's reelection campaign, was forced to resign after being accused by Hansen for barring journalists from interviewing him.
In his book "The Assault on Reason," former vice president Al Gore said that Deutsch, who has no scientific education or university diplomat, wrote a memo to scientists saying that the Big Bang is "not proven fact; it is an opinion."
"This is more than a science issue, it is a religious issue," Deutsch wrote, according to Gore, the former Democratic candidate who lost the 2000 election to Bush.