WASHINGTON (Reuters) - The federal government's media watchdog on Monday promised to investigate whether indecency rules were broken during the broadcast of the Super Bowl halftime entertainment show when pop singer Janet Jackson's bodice was ripped to expose her right breast.

During the break in the National Football League's championship game, singer Justin Timberlake reached for Jackson as they sang a duet and tore off part of her black leather bustier, prompting widespread outrage.

U.S. Federal Communications Commission Chairman Michael Powell promised a quick and thorough investigation of the stunt aired during one of the most popular American television broadcasts, which also attracts a major worldwide audience.

"That celebration was tainted by a classless, crass and deplorable stunt," Powell said in a statement that was echoed by others on the panel. "Our nation's children, parents and citizens deserve better."

Television networks are already on the defensive, with the FCC taking a more aggressive stand against indecency and Congress threatening to sharply raise fines for such incidents.

Viacom Inc.'s CBS, which aired the show, has been under fire in recent months for refusing to air political advertisements during the game and for shunting a controversial movie about former president Ronald Reagan to cable from the broadcast network.

CBS and its other unit MTV, which produced the halftime bonanza, apologized for what they described as an unscripted moment. Timberlake said it was a "wardrobe malfunction."

'BROADCAST STANDARDS'

"We attended all rehearsals throughout the week and there was no indication that any such thing would happen," CBS said. "The moment did not conform to CBS broadcast standards and we would like to apologize to anyone who was offended."

A spokesman for CBS had no immediate comment on the probe and a Viacom spokesman was not immediately available for comment. The NFL said it would not likely allow MTV to produce another halftime show.

The game garnered the best ratings in six years and the incident provoked wall-to-wall coverage on cable news networks.

"I don't really see what the big deal is all about. It's just a boob," said Judy Reeves, 24, who is in public relations.

But complaints flooded into the FCC about Jackson and male singers grabbing their groin area while performing.

The FCC could fine each station that aired the show as much as $27,500 per violation as well as hold hearings on whether to revoke stations' broadcast licenses.

"Whether or not CBS executives did or did not know in advance is irrelevant, Viacom executives had the duty to know." said Parents Television Council President Brent Bozell who urged the FCC to fine each station that aired it the maximum.

Federal rules bar the broadcast of obscene material and limit the airing of indecent material that contains sexual or excretory references in a patently offensive manner to late night hours when children are less likely to be watching.

As part of a tougher stance against indecency at times when children are likely to be watching, the FCC is considering action against General Electric Co.'s NBC television network for an incident in which U2 rocker Bono said "f---ing brilliant" when accepting an award on a live broadcast.