Two powerful congressional Republicans want to know more - a lot more - about why and how Environmental Protection Agency officials have for several years erected multiple obstacles to conservative think tanks, media outlets and non-profit activists filing Freedom of Information Act requests with the agency.

"According to documents obtained by the Committees, EPA readily granted FOIA fee waivers for liberal environmental groups - effectively subsidizing them - while denying fee waivers and making the FOIA process more difficult for states and conservative groups," said Sen. David Vitter and Rep. Darrell Issa in a letter today to EPA's acting administrator, Bob Perciasepe.

"This is a clear abuse of discretion. Consequently, the committees request that you immediately take necessary steps to ensure that such manipulation of the FOIA process does not occur in the future," Vitter and Issa wrote.

Reproduction fees covering multiple documents can easily run into the thousands of dollars, which is why Congress included a liberal waiver provision in the original FOIA it approved in 1966 and which remains in the law today.

Issa, a California Republican, is chairman of the House Oversight and Government Reform Committee, while Vitter, a Louisiana Republican, is the ranking minority member of the Senate Environment and Public Works Committee.

Their concern about EPA's disparate handling of FOIA requests from conservative and liberal requestors was initially sparked by research by Competitive Enterprise Institute Senior Fellow Christopher Horner.

Horner, a long-time critic of EPA and liberal environmental policies, published a book - The Liberal War Against Transparency - last year in which he revealed the use of private email accounts to do official business by EPA officials beginning in the Clinton administration under administrator Carol Browner.

Federal officials are required to disclose such email use to agency FOIA staffs to insure their content is included where appropriate in responses to FOIA requests.

As first reported earlier this week by The Washington Examiner's Michal Conger, a review by committee staff of more than 1,200 FOIA fee waiver requests found that EPA officials waived reproduction fees requested by environmental groups that favor bigger government programs 92 percent of the time.

Fee waiver requests from conservative groups that favor limited government programs, however, were rejected by EPA officials by virtually the same percentage.

Among the favored groups were the Natural Resources Defense Council, Earth Justice, Public Employees for Environmental Responsibility and the Center for Biological Diversity.

Besides CEI, the groups discriminated against by EPA included the Institute for Energy Research, Judicial Watch, the National Center for Public Policy Research and the Franklin Center for Government and Public Integrity.

"The startling disparity in treatment strongly suggests EPA's actions are possibly part of a broader effort to collude with groups that share the agency's political agenda and discriminate against states and conservative organizations. This is a clear abuse of discretion," Vitter and Issa said in their letter.

"Consequently, the Committees request that you immediately take necessary steps to ensure that such manipulation of the FOIA process does not occur in the future," they said.

The EPA inspector general has opened an investigation into the agency's fee waiver policies and procedures.

In the meantime, the two congressmen requested that EPA provide them with copies of all FOIA fee waiver requests on a monthly basis, as well as copies of all documents, including internal emails and memos, concerning such requests from Jan. 21, 2009, through May 16, 2013.

Mark Tapscott is executive editor of The Washington Examiner. He can be reached at