Two federal agencies are investigating whether the Bush administration tried to block government scientists from speaking freely about global warming and censor their research, a senator said Wednesday.

Sen. Frank Lautenberg, D-N.J., said he was informed that the inspectors general for the Commerce Department and NASA had begun "coordinated, sweeping investigations of the Bush administration's censorship and suppression" of federal research into global warming.

"These investigations are critical because the Republicans in Congress have ignored this serious problem," Lautenberg said.

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He said the investigations "will uncover internal documents and agency correspondence that may expose widespread misconduct."

He added, "Taxpayers do not fund scientific research so the Bush White House can alter it."

Messages left Wednesday at the offices of the inspectors general, which serve as the agencies' internal watchdogs, were not immediately returned.

Kristen Hellmer, a spokeswoman for the White House Council for Environmental Quality, said Wednesday night that the administration has supported the scientific process in its approach to studying climate change.

"We have in place the most transparent system of science reporting, and claims that the administration interfered with scientists are false," Hellmer said. "Our focus is on taking action and making real progress in reducing greenhouse gas emissions. The nearly $2 billion worth of climate science we publish annually leads the world and speaks for itself."

Carbon dioxide and other gases primarily from fossil fuel-burning that scientists say trap heat in the atmosphere have warmed the Earth's surface an average 1 degree over the past century.

The White House has committed to reducing the "intensity" of U.S. carbon pollution, a measure of the amount of carbon dioxide emitted per unit of economic growth.

But the total of U.S. emissions, now more than 7 billion tons a year, is projected to rise 14 percent from 2002 to 2012.

In February, House Science Chairman Sherwood Boehlert, R-N.Y., and other congressional leaders asked NASA to guarantee scientific openness.

They complained that a public-affairs officer changed or filtered information on global warming and the Big Bang, the prevailing theory regarding the origin of the universe.

The officer, George Deutsch, a political appointee, had resigned after being accused of trying to limit reporters' access to James Hansen, a prominent NASA climate scientist, and insisting that a Web designer insert the word "theory" with any mention of the Big Bang.

A report last month in the scientific journal Nature claimed administrators at the Commerce Department's National Oceanic and Atmospheric Administration blocked the release of a report that linked hurricane strength and frequency to global warming.

Hansen had said in February that NOAA has tried to prevent researchers working on global climate change from speaking freely about their work.

NOAA has denied the allegations, saying its work is not politically motivated.