WASHINGTON (Reuters) - Democratic senators called on Tuesday for the resignation of Stephen Johnson, head of the U.S. Environmental Protection Agency, saying he sided with polluters instead of fighting global warming and other ecological problems.

The three senators, all active in the climate change debate, also asked the U.S. attorney general to investigate whether Johnson has made false or misleading statements in sworn testimony before the Senate's Environment and Public Works Committee.

Boxer, who heads the environment committee, said Johnson had made damaging decisions on mercury, lead, toxic chemicals, drinking water standards, ozone air pollution and global warming.

She said these decisions were "harmful to the American people."

Boxer noted that last year, Johnson denied California's request for federal permission -- known as a waiver -- to impose tough new limits on climate-warming carbon dioxide emissions from cars and light trucks. That decision effectively blocked as many as 18 other states from doing the same.

Boxer, Sen. Sheldon Whitehouse of Rhode Island and Sen. Amy Klobuchar of Minnesota wrote to Attorney General Michael Mukasey, asking him to investigate Johnson, specifically noting the California waiver decision.

"False testimony by any witness is serious and undermines our ability to fulfill our constitutional duties on behalf of the American people," the senators wrote. "Our concern is heightened because this decision by the EPA administrator affects the health and well-being of the American people."

White House spokesman Tony Fratto dismissed the allegations against Johnson, saying Boxer has "no standing" to question Johnson's integrity.

"Administrator Johnson is an honorable, experienced, career scientist and everything he has done at the EPA has been with the interests of protecting the American people and our environment," Fratto said.

(Editing by Eric Walsh)

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