Agency staff warned Johnson that rejecting the limits could prompt lawsuits that the agency would lose, according to the memo to members of the House (of Representatives) Oversight and Government Reform Committee.

The memo, written by staff for the Democratic majority on the committee, said documents and interviews with agency officials shows these officials unanimously recommended that California's request be granted.

Johnson initially favored doing so, at least in part, but "reversed his position after communications with officials in the White House." The state wanted the tougher emissions standards to help fight climate change.

"The record before this committee suggests that the White House played a pivotal role in the decision to reject the California petition, but it does not explain the basis for the White House intervention," the memo said.

To impose tougher pollution standards than the federal government's, California must get a so-called waiver from the EPA. Such waivers have customarily been granted.

But Johnson rejected California's request, saying its pollution problems did not merit special consideration.

California is leading a suit to reverse the EPA decision.

'BEST OF A BAD LOT'

Eighteen other states also favoured California's proposed greenhouse gas standards, which would have forced automakers to cut emissions by making vehicles much more fuel-efficient starting in 2009.

The memo quoted from briefing materials prepared for Johnson as he considered the waiver. When asked specifically to offer options that included turning the waiver down, agency lawyers did so, but offered a "caveat," the memo said.

"After review of the docket and precedent, we don't believe there are any good arguments against granting the waiver," the caveat read. "All of the arguments discussed here are likely to lose in court if we are sued. The arguments here are the best of a bad lot, going from most to least plausible."

Jonathan Schradar, an EPA spokesman, dismissed the memo as old news.

"I equate this to deciding whether to wear a red tie or a blue tie in the morning," Schradar said by telephone. "It doesn't make much difference until I put the tie on. To go through and suggest that maybe (Johnson) had a different opinion during the process -- none of that matters."

The White House Council on Environmental Quality also referred to Johnson's statements in denying the waiver.

The memo by the House oversight committee, chaired by California Democratic Rep. Henry Waxman, said "further investigation will be required to assess the legality of the White House role in the rejection of the California motor vehicle standards."

In the Senate, where climate change legislation is set for debate in June, Sen. Barbara Boxer, a California Democrat who chairs the Environment and Public Works Committee, called the administration's decision "indefensible."