The hostility between the Fox News Channel and its television news competitors, usually barely submerged, exploded into open recriminations Friday over a newspaper advertisement in which Fox accused its competitors of missing the story of the so-called antitax protests in Washington last Saturday.

All of the other networks named  CNN, MSNBC, ABC News, NBC News and CBS News  issued statements and details about the extent of their coverage. The networks accused Fox News, a channel with a reputation for having a conservative point of view in much of its programming, of putting blatantly false information in the ad, which ran in three papers: The Wall Street Journal, The Washington Post and The New York Post.

Most vocal was CNN, whose executives approved an on-the-air denunciation of the Fox ad by one of its anchors, Rick Sanchez, who addressed Fox News directly, included extensive clips of the coverage CNN provided that day, and said Fox was criticizing its competitors because they did not choose to promote the event, as he said Fox had.

“Here’s the fact,” Mr. Sanchez said. “The bottom line is we do cover the news and we did extensively cover this event. We didn’t promote the event. That’s not what real news organizations are supposed to do.”