Progressive activists and public interest groups have long blasted Rupert Murdoch and his News Corporation for political biases. But in recent weeks they have seized on a new and more tangible reason to call for the revocation of his TV licenses and the breakup of his company: the British hacking scandal.

A list of Rupert Murdoch's media holdings was shown Thursday on “The Colbert Report.” The scandal, they say, is an opportunity to raise awareness of — and, they hope, objection to — media consolidation at a time when the American government is reviewing the rules that govern how much companies like News Corporation, Comcast and the Walt Disney Company can own.

“For those of us who’ve been warning about the dangers of too much media power concentrated in too few corporate hands, this scandal is a godsend,” said Jeff Cohen, the founding director of the Park Center for Independent Media at Ithaca College.

The scandal is also giving Democratic lawmakers an opportunity to call for more attention to the practices of such companies.

Representative Bobby Rush, a Democrat of Illinois and a past critic of Mr. Murdoch, questioned in an interview whether the media mogul had been allowed to amass too much media power. “We can’t forget the fundamental tenet of media ownership in the United States. It’s not a right, it’s a privilege. And it’s a privilege based on trust and responsibility,” he said.

Representative Tammy Baldwin, a Democrat of Wisconsin, said that along with media consolidation, the scandal raised questions about “privacy expectations in the digital world” and about how “we support freedom of the press while ensuring the integrity and truthfulness of the press.”

There are few if any immediate threats to Mr. Murdoch’s American portfolio, which includes the Fox network, two dozen local television stations, The Wall Street Journal, The New York Post and the 20th Century Fox movie studio. The Federal Communications Commission signaled last week that it regarded the hacking scandal as isolated to Britain.

But the scandal in Britain could influence the F.C.C. review of media ownership rules, especially if there is perceptible public discord about powerful media moguls like Mr. Murdoch.

The discord is already evident in Britain, where politicians have talked openly about considering new laws that would lead to a breakup of the News Corporation, which owns 39 percent of British Sky Broadcasting as well as numerous newspapers there.

In the United States, politicians have called for investigations into whether News Corporation entities hacked into the phones of Americans, including the victims of Sept. 11 terrorist attacks. The Federal Bureau of Investigation is now investigating; on Tuesday, Mr. Murdoch said that he was aware of no evidence that any 9/11 American victims had been affected.

But media reform groups like Free Press, which advocates for more diversity in media ownership, say their interest extends far beyond any single investigation.

“I think this is the moment to contend with the serious damage the Murdoch empire has done to our media system over the past few decades,” Craig Aaron, the head of that group, said last week.

The 2004 book “The New Media Monopoly” by Ben H. Bagdikian found that more than half of the radio and television stations, daily newspapers, magazines, publishers and movie studios in the United States were owned by five companies. In January, in the most recent case of consolidation, the government approved a bid by Comcast to take control of NBC Universal.

Proponents of media mergers say such combinations improve consumer access to news, information and entertainment. They say the Internet has fostered competition, creating new choices for consumers.

Groups like Free Press say the opposite — that such combinations reduce the country’s journalistic corps and decrease the diversity of voices in print and on the air. Mr. Aaron said he sensed that most Americans were aware of big media brands like Fox and NBC but unaware that their owners also controlled dozens of other brands. Media companies present an obstacle to awareness: “Most media outlets don’t like to cover themselves.”

But “when people find out just how much those companies own, they are worried about it and want to know more,” he said, adding that the who-owns-what chart was the most popular feature on the Free Press Web site.

This week, the F.C.C. declined to comment on the status of its ownership review, which is supposed to assess whether the existing rules are effectively promoting diversity, localism and competition. Earlier this month, an appeals court upheld most of the steps that the commission took in 2007 to loosen ownership rules, but it rejected on procedural grounds one rule that enabled more companies to own a newspaper and a station in the same local market.

Cable outlets like Fox News — the scourge of liberals and a symbol of Mr. Murdoch’s political power — are not under the purview of the F.C.C. or its ownership review, but the News Corporation’s 27 local stations are, because each is dependent on a federal license for use of the public airwaves.

License revocations are extremely rare, and analysts said they did not anticipate problems for the stations as a result of the hacking scandal. But an F.C.C. provision assessing the character of a station owner could be invoked by the News Corporation’s opponents when the company’s licenses for Fox and MyNetwork stations come up for renewal.

The broader problem for Mr. Murdoch, Mr. Aaron suggested, is that he “had an air of invincibility” before the scandal became one of the most talked-about news stories in Britain and the United States. “Whatever happens now, that’s gone,” he said.

Andrew Jay Schwartzman of the public interest group Media Access Project, said he doubted that loyal viewers of Fox News, a News Corporation property, would change their views.

But, he added, “a much larger group of people have an instinctive mistrust of powerful media, and they understand that consolidation of media ownership is not good for democracy.”

“For better or worse,” Mr. Schwartzman said, “News Corporation’s misdeeds will fuel that skepticism.”