Fox News Channel has long needled its critics with its omnipresent slogan: “Fair and Balanced.” Now, some of its opponents are making a federal case out of it.

Advocacy groups MoveOn.org and Common Cause filed a petition with the Federal Trade Commission yesterday alleging that Fox’s use of the slogan is deceptive advertising. The groups call for a cease-and-desist order to stop Fox from continuing to use the trademarked phrase.

“When a news outlet is allowed to blur the lines between opinion and journalism and call it ‘fair and balanced,’ I think it’s confusing to consumers of information in this country and it’s damaging to democracy,” said the president of Common Cause, Chellie Pingree.

Reached for comment, a Fox spokesman was as blunt as any of the network’s top anchors.

“Here’s what we’ll comment about this: It was a transparent publicity stunt. We recognize all forms of free speech in this country and we wish them well,” said the spokesman, Robert Zimmerman. He declined to answer any other questions.

The petition argues that Fox News’s programming is biased, distorted, and manipulated to promote the Bush administration and the Republican Party. It cites several studies contending that Fox’s coverage is imbalanced and its viewers misinformed about significant events, including the war in Iraq.

Also used as evidence are interviews from “Outfoxed,” the MoveOn.org sponsored documentary released last week that aims to expose Fox’s alleged bias.

“My only gripe with Fox is they made ‘fair and balanced’ nothing more than an arrogant and cynical parody of journalism,” David Korb, one of the former Fox employees who criticizes the network in “Outfoxed,” said yesterday.

“That phrase, ‘fair and balanced,’ is entirely misdescriptive,” said Don Hazen of the Independent Media Institute. The San Francisco-based nonprofit group has filed its own petition against Fox, asking the U.S. Patent and Trademark Office to cancel the network’s trademark of the phrase.

MoveOn’s move isn’t the first time “fair and balanced” has spurred legal controversy.

Last August, Fox filed suit to stop publication of Al Franken’s satirical book, “Lies, and the Lying Liars Who Tell Them: A Fair and Balanced Look at the Right,” claiming that Franken’s use of the trademarked slogan would “blur and tarnish” the network.

The suit was summarily thrown out by District Court Judge Denny Chin, who called the case “wholly without merit, both factually and legally.”

The FTC petition may be following the same futile path. Prominent media scholars are skeptical of the attempt to turn criticism of Fox News into, well, a federal case.

“My guess is in the end, this isn’t going to go much further than the last case that brought ‘fair and balanced’ into the courtroom,” said Robert Thompson, director of the Center for the Study of Popular Television at Syracuse University, referring to the Franken case. “I seriously doubt that Fox is going to be called to task.”

“I don’t like to see government stepping on and telling media organizations or persons what they can say or they can’t say,” said Paul Levinson, head of the department of communications and media studies at Fordham University. “The greater interest in a free society is keeping federal hands off of political communities.”

Mr. Levinson said that he thought “fair and balanced” was a “ludicrous slogan,” but “to say Fox can’t use it, I think that goes way too far.”

Jay Rosen, chairman of the journalism department at New York University, was also wary of federal intervention.

“I would prefer that ‘fair and balanced’ as a slogan be defeated in the marketplace of ideas if it deserves such,” he said. “Using the government to get them to stop is not something I support.”

Following the announcement of the filing, officials from MoveOn.org and Common Cause affixed copies of the petitions to a ground-floor window at Fox News’s New York headquarters, the News Corporation building at 1211 Avenue of the Americas.

A small group of MoveOn.org members then distributed DVDs of “Outfoxed” to Fox News employees as they entered and departed the building.

The petitions themselves were left to flap in the wind. Few passersby stopped to inspect them further.