Amid conflict over the political content of its programming, the Public Broadcasting Service yesterday unveiled editorial standards intended to ensure balance and fairness in its news, science and documentary shows.

Separately, Alexandria-based PBS also said it would hire an ombudsman for the first time to review controversial programs after they air.

Officials said both moves were initiated before public broadcasting in general, and PBS in particular, came under fire in recent months from the head of a primary funding organization. But both actions, at the very least, could help PBS dispel the impression that it is unresponsive to its critics just as Congress is considering public broadcasting's federal funding for next year.

Kenneth Y. Tomlinson, chairman of the Corporation for Public Broadcasting -- the agency that passes those federal funds to public broadcasters -- has recently asserted that PBS ignores or marginalizes conservative viewpoints. Last week, a Republican-dominated House subcommittee voted to slash federal support of public broadcasting by 25 percent overall, and to eliminate money for children's educational programming, satellite technology and digital-signal improvements. Public broadcasters are lobbying to get the money restored.

One measure of the political sensitivity now surrounding public broadcasting: With yesterday's announcement, there will be four ombudsmen monitoring PBS and National Public Radio. Two of the four were installed at the funding agency, CPB, at Tomlinson's suggestion.

PBS appointed a panel of journalism experts last year to update its editorial policies, the first such review since the standards were adopted in 1987. The panel's recommendations, which were adopted by PBS's board yesterday, probably won't be noticeable to the average viewer, said Jacoba Atlas, PBS's top programming official.

"The good news is that our producers have absolutely been meeting the standards of accuracy, fairness and trust set forth in 1987, and you can see that reflected in every [viewer] poll that has been taken about PBS," she said.

Yet the new standards could still prove to be a source of contention. The CPB must review and accept them before it will release $23 million in funds for PBS's National Program Service (NPS), which includes online content and the shows "NewsHour With Jim Lehrer," "Nova" and "American Experience." If CPB rejects the guidelines, NPS funding that is supposed to begin in October would be jeopardized.

Disagreement flared earlier this year when CPB officials suggested that PBS should provide balancing comments in all programs containing editorial viewpoints and opinions. PBS countered that such a standard was impractical and that the goal could be better met with a variety of programs that, when taken together, would achieve political balance. The dispute was settled when both sides agreed NPS funding would be contingent on CPB accepting the new standards. CPB officials will review the guidelines within the next several weeks.

Among the few changes in the editorial standards are a commitment by PBS program producers to offer additional "transparency" in describing their journalistic methods and conclusions, said Tom Rosenstiel, who drafted the advisory panel's final recommendations. In other words, he said, viewers might learn more about how reporters or documentary makers went about gathering their material and the editorial decisions they made in presenting it.

"I'd be surprised if this led producers to do things in a dramatically different way," said Rosenstiel, director of the Project for Excellence in Journalism, funded by the Pew Charitable Trusts. "But hopefully it will make more of the work more easily understood, especially where controversial or difficult choices were made."

Atlas and Rosenstiel differed on how a provision requiring the labeling of commentary or opinion might be applied on PBS programs. Rosenstiel said a program such as "The Journal Editorial Report" -- in which conservative editorial writers from the Wall Street Journal discuss the news -- would need to be labeled. But Atlas said: "That's an interesting question. We've looked into that. The name spells out that it's opinion, so it's already labeled. But if there's a perception that the name doesn't make that clear, we'll look into it further."

The Wall Street Journal program was championed by Tomlinson, the CPB's chairman, who advocated that CPB use its own funds to produce it.

Atlas added that any commentary by veteran PBS journalist and commentator Bill Moyers would be labeled as such if Moyers -- who drew the wrath of Tomlinson for alleged liberal bias -- "turns to the camera and says, 'I think we should do X, Y and Z' " on "Wide Angle," a program Moyers will join in July.