Tomlinson, a Republican, quit shortly before CPB Inspector General Kenneth Konz was to publish a report after investigating his activities, including paying outside researchers to check public programing for liberal bias.

Critics, including broadcasters and congressional Democrats, accused Tomlinson of trying to advance his own conservative agenda in public broadcasting, which is supposed to be non-partisan.

Details of the investigation have not yet been reported. It also looked into the selection of a former co-chair of the Republican National Committee as CPB president, according to Sen. Byron Dorgan (news, bio, voting record), a North Dakota Democrat.

The CPB said both the board and Tomlinson believed it was in the best interest of the CPB that he step down.

"The board does not believe that Mr. Tomlinson acted maliciously or with any intent to harm CPB or public broadcasting, and the board recognizes the Mr. Tomlinson strongly disputes the findings in the soon-to-be-released inspector general's report," the board said in a statement.

The board commended Tomlinson for "his legitimate efforts to achieve balance and objectivity in public broadcasting."

During a Senate hearing in July on CPB's funding, Tomlinson defended his hiring of outside lobbyists, saying they were needed to temporarily augment his agency's small staff.

CPB is a federally funded nonprofit corporation and the largest single source of money for U.S. public television and radio programing, including PBS and National Public Radio. It is governed by a presidentially appointed board.

Center for Digital Democracy Executive Director Jeff Chester, a critic of Tomlinson, said his departure was unlikely to stop what he described as behind-the-scenes programing pressure on PBS and NPR.

"Board chair Halpern and vice chair Gaines will continue Tomlinson's legacy to reshape public broadcasting more to the liking of conservatives," Chester said in a statement.

Veteran Republican Party fund-raisers Cheryl Halpern and Gay Hart Gaines were elected in September as CPB board chairman and vice chair, respectively.