WASHINGTON — Researchers who work for Congress say the Environmental Protection Agency skewed its analysis of air pollution legislation to favor President Bush's plan.

EPA's analysis "works in favor of" Bush's plan by overstating some costs of competing bills, said a report Friday by the Congressional Research Service. The 2002 Bush plan, dubbed "Clear Skies," remains stalled in Congress.

"Although it represents a step toward understanding the impacts of the legislative options, EPA's analysis is not as useful as one could hope," the report concludes.

It took three years for EPA to provide comparisons of Bush's plan with competing versions by Sens. Tom Carper, D-Del., and James Jeffords, I-Vt.

When it did in October, the EPA said its analysis showed the superiority of the Bush proposal, which relies on market forces to cut pollution from the nation's 600 coal-burning power plants but does not address global warming.

EPA officials dismissed any notion of playing favorites.

"It does a real disservice to this discussion to have an analysis that makes unfounded and inaccurate conclusions," agency spokeswoman Eryn Witcher said.

She said Bush's plan builds on new EPA rules "which is why we have been urging Congress to pass a permanent, nationwide solution and have gone the extra mile to provide the most detailed, thorough, comprehensive legislative analysis of air ever prepared by the agency."

The EPA also had projected a broad range of potential costs if the United States were to regulate carbon dioxide, a gas produced by the burning of fossil fuels that many scientists blame for global warming.

But along with aiming to reduce carbon dioxide, the competing bills would force industry to install more high-tech pollution controls to cut emissions of three main pollutants from power plants: nitrogen oxides, which form smog; sulfur dioxide, which causes acid rain; and mercury, a neurotoxin that accumulates in fish and works its way up the food chain.

But the agency overestimated costs of installing the high-tech controls for mercury and assumes natural gas will more plentiful and available at cheaper prices than the Energy Department estimates, according to congressional researchers James McCarthy and Larry Parker.

Proponents of Bush's approach have repeatedly argued that stricter controls like those sought by Carper and Jeffords could harm coal-producing states in the Midwest and East by forcing more power plants to switch from coal to natural gas.

EPA estimated that Bush's plan would cost utilities up to $6 billion a year, compared with up to $10 billion under Carper's bill and as much as $51 billion in Jeffords'. Bush's bill provides $143 billion a year in health benefits, EPA said, compared with $161 billion under the Carper bill and $211 billion in the Jeffords bill.

Source: Associated Press