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

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

Johnson’s decision also blocked more than a dozen other states, including Maine and Massachusetts, 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 EPA, frequently has denied that his decisions are being directed by the White House. “I am the decision-maker,” Johnson said Monday, meeting with reporters before the California waiver report surfaced.

A White House spokeswoman denied interference.

“No,” said Kristen Hellmer, spokeswoman for the White House Council on Environmental Quality, when asked whether the White House sought to influence Johnson on the California waiver. “He made an independent decision.”

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

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

Deposed 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 two or three 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 Gov. Arnold Schwarzenegger announcing the rationale for denying the waiver, and into the formal decision document released in February.

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

Burnett refused to answer questions about who Johnson talked to and when, saying EPA told him not to.

Also, EPA continues to withhold documentation of telephone calls and meetings in the White House, the committee said. The White House Counsel’s Office told committee investigators EPA has 32 such documents described as “indicative of deliberations at the very highest level of government.”

“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.”

EPA spokesman Jonathan Shradar 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,” Shradar said. He did not respond when asked if it was true Johnson initially supported the waiver.