WASHINGTON - The head of the Environmental Protection Agency initially supported giving California full or partial permission to limit tailpipe emissions - but reversed himself after hearing from the White House, according to a report yesterday.

The report by the Democratic staff of the House Oversight and Government Reform Committee, which cites sworn depositions by high-level EPA officials, amounts to the first solid evidence of the political interference alleged by Democrats and environmentalists since the EPA administrator, Stephen Johnson, denied California's waiver request in December.

Johnson's decision also blocked more than a dozen other states, including Massachusetts and Rhode Island, that wanted to follow California's lead and regulate greenhouse gas emissions from cars and trucks. It was applauded by the auto industry and supported by the White House, which has adamantly opposed mandatory caps on greenhouse gas emissions.

Johnson has defended the December decision as his alone. He has refused to say whether there was White House pressure.

Although California had never previously been fully denied a waiver request under the Clean Air Act, Johnson justified denying this one on the basis that California is not alone in suffering the effects of global warming and therefore doesn't have a compelling need for its own greenhouse gas standards. EPA spokesman Jonathan Shradar dismissed the report by the committee, chaired by Representative Henry Waxman, Democrat of California, as "nothing new."

"Administrator Johnson was presented with and reviewed a wide range of options and made his decision based on the facts and the law," Shradar said. "Distraction-oriented, political tactics of the committee will not keep EPA from moving forward, tackling tough issues and putting into place the most health-protective standards ever."

Shradar did not respond when asked whether it was true Johnson initially supported fully or partially granted the waiver request.

California's law would have forced automakers to cut greenhouse gas emissions by 30 percent in new cars and light trucks by 2016, beginning with the 2009 model year.

In the course of its investigation the committee issued three subpoenas, received more than 27,000 pages of documents and deposed eight EPA officials.

The committee found, as has been previously reported, that the EPA's career staff was unanimously in favor of at least partly granting the California waiver and advised Johnson that any other decision was unlikely to stand up in court.

The most explosive new evidence came from a deposition with EPA associate deputy administrator Jason Burnett.

Under oath, Burnett told committee staff that Johnson "was very interested in a full grant of the waiver" in August and September of 2007 and later thought a partial grant - allowing the waiver for the first two or three model years - "was the best course of action."

Johnson's position changed after Johnson communicated with the White House, Burnett said.

Burnett also said there was White House input into the December letter to Governor Arnold Schwarzenegger announcing the rationale for denying the waiver, and into the formal decision document released in February.

However the committee was stymied in its attempts to discover the extent and rationale for the White House's involvement.

Also, the EPA continues to withhold some documents that show telephone calls or meetings in the White House. The committee report said that the White House Counsel's office has told the panel the EPA has 32 such documents and has described them as "indicative of deliberations at the very highest level of government."

A White House spokesman didn't immediately return a call for comment yesterday.

"It appears that the White House played a significant role in the reversal of the EPA position," the report concludes. "It would appear to be inconsistent with the president's constitutional obligation to faithfully execute the laws of the United States if the president or his advisers pressured Administrator Johnson to ignore the record before the agency for political or other inappropriate reasons."

© Copyright 2008 Globe Newspaper Company.