U.S. Rep Ed Markey, D-Mass., ranking member of the House Natural Resources Committee, called on the Government Accountability Office to study energy subsidies for the oil and gas industry.
"Understanding the totality of these subsidies is imperative in evaluating federal support for energy industries like the oil and gas sector," he wrote in a letter to the GAO.
Markey said his letter is in response to "narrow requests" by Republicans to the GAO that were "written to ignore certain taxpayer support to the oil and gas and nuclear industries."
Democratic leaders have said Republicans are supporting legislation that would diminish the effectiveness of environmental laws.
U.S. President Barack Obama has said he wanted to cut back on tax breaks given to the oil industry, a move countered by trade groups like the American Petroleum Institute. Supporters of a low-carbon economy have expressed concerns about tax credits for the renewable energy sector as lawmakers approach a so-called fiscal cliff, a series of tax benefits set to expire at year's end.
In the letter to the GAO, Markey said Republicans have "narrowly tailored" the definition of what constitutes a subsidy for energy technologies in order to benefit oil and gas.