A House committee chairman on Friday threatened to hold the head of the EPA and a White House budget official in contempt of Congress for not handing over documents about new smog requirements and a decision blocking California greenhouse gas limits.

Democratic Rep. Henry Waxman of California, chairman of the House Government Reform and Oversight Committee, said he'd hold a vote in his committee next week on a contempt resolution, if he doesn't get the information he wants.

He made the threat in letters to EPA Administrator Stephen Johnson and Susan Dudley, administrator for information and regulatory affairs at the White House Office of Management and Budget.

Waxman and others have complained about evidence that the White House intervened with the Environmental Protection Agency to produce more industry-friendly outcomes on both the smog and greenhouse gas issues. Waxman has issued a series of subpoenas to learn more, but weeks have passed and neither EPA nor the Office of Management and Budget has fully complied. Waxman said Friday he'd waited long enough.

"I regret that your failure to produce responsive documents has created this impasse, but Congress has a constitutional duty to conduct oversight of the executive branch," he wrote to both officials.

"Therefore, unless the documents are provided to the committee or a valid assertion of executive privilege is made, the committee will meet on June 20 to consider a resolution holding you in contempt," Waxman wrote.

EPA spokesman Jonathan Shradar said his agency has turned over tens of thousands of documents to Waxman "and there has been no wrongdoing uncovered."

"The committee seems to be on a political hunt that will leave them wanting yet again," Shradar said in a statement.

OMB spokeswoman Jane K. Lee called Waxman's move "unfortunate" and said the office that Dudley heads "has gone to great lengths to cooperate with the committee, providing voluminous documents on an expedited basis (more than 7,500 pages)."

Johnson has consistently maintained that he was the one who made the final decisions on the smog rule and the California greenhouse gas waiver.

The EPA in March issued tougher health standards for ozone, commonly known as smog, but they weren't as tough as recommended by an EPA science advisory board and many health experts.

The EPA also did not go as far as the science panel had recommended in setting a separate standard to protect the environment from smog. EPA and White House officials have acknowledged that a tougher standard had been opposed by the Office of Management and Budget and the issue was settled after President Bush intervened directly on behalf of the White House staff only hours before the rule was announced.

On the California greenhouse gas issue, Waxman's committee staff produced a report last month concluding from interviews with high-level EPA officials that Johnson initially supported giving California full or partial permission to limit tailpipe emissions — but reversed himself after hearing from the White House.

More than a dozen other states were also blocked from implementing the tailpipe emission limits after Johnson rejected California's request for a required federal waiver in December.