By Jonathan Amos
Science reporter, BBC News, San Francisco
Some 10,000 US researchers have signed a statement protesting about political interference in the scientific process.
There have been claims of political interference on climate issues
The statement, which includes the backing of 52 Nobel Laureates, demands a restoration of scientific integrity in government policy.
According to the American Union of Concerned Scientists, data is being misrepresented for political reasons.
It claims scientists working for federal agencies have been asked to change data to fit policy initiatives.
The Union has released an "A to Z" guide that it says documents dozens of recent allegations involving censorship and political interference in federal science, covering issues ranging from global warming to sex education.
Campaigners say that in recent years the White House has been able to censor the work of agencies like the Environmental Protection Agency and the Food and Drug Administration because a Republican congress has been loath to stand up for scientific integrity.
"It's very difficult to make good public policy without good science, and it's even harder to make good public policy with bad science," said Dr Peter Gleick, president of the Pacific Institute for Studies in Development, Environment and Security.
"In the last several years, we've seen an increase in both the misuse of science and I would say an increase of bad science in a number of very important issues; for example, in global climate change, international peace and security, and water resources."
The statement was released at the American Geophysical Union's Fall Meeting. It is an annual gathering of Earth scientists.
Last year, it triggered a major row when a discussion here resulted in the renowned US space agency climate scientist Dr James Hansen later claiming he had come under pressure not to talk to the media on global warming issues.
Michael Halpern from the UCS said the statement of objection to political interference had been supported by researchers regardless of their political views.
"This science statement that has now been signed by the 10,000 scientists is signed by science advisers to both Republican and Democratic administrations dating back to President Eisenhower, stating that this is not business as usual and calling for this practice to stop," he told BBC News.
The Union said is was hopeful that the new Congress taking office in January would show a greater commitment to protecting the integrity of the scientific process.