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

"EPA's analysis is not as useful as one could hope," the report concludes.

It took three years for the EPA to provide comparisons of Bush's plan with competing versions by senators Tom Carper and James Jeffords.

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 600 coal-burning power plants in the U.S., but does not address global warming.

EPA officials dismissed any notion of playing favourites.

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