The Public Broadcasting Service does not allow political pressure to influence content decisions, PBS President Pat Mitchell said Tuesday, defending the public television network from accusations of liberal bias.

"PBS has stood steadfastly resolved not to give in to those pressures and that resolve is rock solid today," she told an audience of media members at the National Press Club (search).

"PBS does not belong to any one political party," she added.

Mitchell was responding in part to efforts by Ken Tomlinson, president of the Corporation for Public Broadcasting, to add more conservative programming to PBS' line up to balance what he calls liberal advocacy shows such as "NOW," which used to be hosted by Bill Moyers (search).

Tomlinson was elected chairman of CPB — the agency that oversees tax money given to and marketing of PBS and National Public Radio — in 2003 after being appointed by President Clinton and confirmed by the Senate in 2000. He told FOX News last week that he thinks a variety of programming would appeal to more viewers.

"On some levels, I am mystified by the controversy because how can any segment of the American people be opposed to common-sense balance?" he asked.

On Tuesday, Mitchell indicated she's not buying Tomlinson's premise that PBS lacks balance.

"The facts do not support the case he makes," she said. "The public opinion surveys including CPB's own survey are very clear that the American public by a large majority, 80 percent, does not perceive bias in PBS' programming, and that seems to me to rest the case."

But Tomlinson said shows such as the "Journal Editorial Report," which he championed and which includes panelists from the Wall Street Journal's conservative editorial page, offer an alternative to Moyers' show.

For his part, Moyers said Tuesday that he is a liberal, but he isn't pleased with Tomlinson's assessment of Moyers' work on "NOW" as liberal advocacy. He called that assessment unfounded and unseemly.

"The president of the Corporation for Public Broadcasting shouldn't be attacking or discrediting our individual journalists," Moyers said.

At the end of Mitchell's speech, a representative of the club handed Mitchell a thank-you plaque. Her revealing response suggested just how much she does not want people to make a mistake about her association with CPB.

"I hope you won't take it as a criticism. It says Corporation for Public Broadcasting. I think this kind of points up our problem," she said to laughs.

The questions about what is "balanced programming" continue. At the Press Club, one person asked Mitchell why PBS doesn't offer a show focusing on labor and consumer issues to balance out the Journal Editorial Report.

Click in the box near the top of the story to watch a report by FOX News' Molly Henneberg.