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

The report by the Democratic staff of the House Oversight and Government Reform Committee cites sworn depositions by high-level EPA officials. Democrats and environmentalists have alleged political interference in the decision since Administrator Stephen Johnson denied California's waiver request in December.

Johnson's decision also blocked Pennsylvania, New Jersey and other states 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 opposed mandatory caps on greenhouse-gas emissions.

Johnson, a 27-year veteran of the EPA, frequently has denied that his decisions are being directed by the White House, and an agency spokesman yesterday dismissed the report 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," said spokesman Jonathan Shradar.

Asked if it was true that Johnson initially fully supported or partially granted the waiver, he didn't respond.

Kristen Hellmer, spokeswoman for the White House Council on Environmental Quality, said Johnson "made an independent decision."

That's not what staff of the oversight committee, chaired by California Democratic Rep. Henry A. Waxman, concluded after deposing eight EPA officials and reviewing more than 27,000 pages of EPA documents, some obtained under subpoena.

Perhaps the strongest evidence came from Associate Deputy Administrator Jason Burnett, a political appointee.

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

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

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

The committee was stymied in efforts to discover the extent and rationale for White House involvement. Burnett did not answer questions on whom Johnson talked to and when, saying the EPA told him not to do so.