WASHINGTON  Congressional Republicans on Wednesday opened a formal assault on the authority of the Environmental Protection Agency to regulate greenhouse gases, raising doubts about the legal, scientific and economic basis of rules proposed by the agency.

The forum was a hearing convened by the energy and power subcommittee of the House Energy and Commerce Committee to review the economic impact of pending limits on carbon dioxide and other heat-trapping gases. But much of the discussion focused instead on whether climate science supports the agency’s finding that greenhouse gases are a threat to health and the environment; that finding is what makes the gases subject to regulation under the Clean Air Act.

Lisa P. Jackson, the E.P.A. administrator, was subjected to more than two hours of questioning, some of it hostile, about proposed limits on emissions from factories, refineries, power plants and vehicles.

Republican lawmakers asserted that the science underpinning the regulatory effort was a hoax, questioned the agency’s interpretation of a Supreme Court decision giving it power to regulate carbon dioxide, and accused the Obama administration of sacrificing American jobs in its misplaced zeal to address climate change.