Sen. Barbara Boxer is asking the Attorney General to investigate whether EPA Administrator Stephen L. Johnson made false or misleading statements in testimony to the Environment and Public Works Committee, which she chairs.

“We do not make this request lightly. However, we believe that there is significant evidence to suggest that Mr. Johnson has provided statements that are inconsistent with sworn testimony and documents provided in connection with an investigation conducted by this committee,” Boxer, D-Calif., and Sheldon Whitehouse, D-R.I., wrote in a letter on Tuesday to Attorney General Michael B. Mukasey.

The lawmakers are referring to questions surrounding Johnson’s decision late last year to block California from regulating greenhouse gases from motor vehicles. They allege that in Jan. 19 testimony, Johnson was not forthcoming about the role of the White House in making this decision.

“Johnson tried very hard to convince us that the California waiver was denied based on decisions that were ‘mine and mine alone,’” Whitehouse said.

The senators believe this contradicts subsequent testimony to the committee by Jason Burnett, a one-time EPA official who resigned in protest. According to Burnett, Johnson had concluded that he would allow the California standard to go forward, until the White House “clearly articulated” that Johnson should deny the request.

“It appears that Mr. Johnson’s account of the California waiver decision is factually inaccurate or misleading,” the senators wrote. “We take the inconsistency between Mr. Johnson’s testimony and other evidence very seriously.”

But Jonathan Shradar, an EPA spokesman, defended Johnson’s actions.

“Administrator Johnson’s record is one of aggressive, health protective environmental standards,” said Shradar said. “Senator Boxer’s record is one of press conferences and political tirades. The administrator’s comments to Congress are honest and he will continue to lead the agency undistracted by the Boxer show.”

Senate Judiciary Chairman Patrick J. Leahy, D-Vt., had intended to question Johnson about his previous testimony at a Judiciary hearing Leahy had scheduled for this week. However, the hearing was canceled after Johnson declined to testify.

Speaking to reporters, Boxer also called on Johnson to resign. She cited a series of controversial decisions since he took office in 2005, including new standards for ozone and lead pollution that Boxer said do not protect public health. This month, the EPA sought additional public comment on how to respond to a 2007 Supreme Court decision on global warming, a step critics view as a delay tactic.

“The EPA has issued one decision after another that leaves families, communities and children in harm’s way,” Boxer said.

“If we can’t trust the top EPA official to tell the truth to the American people, then he must go,” said Amy Klobuchar, D-Minn.