An unfair labor practices complaint filed against Hollywood studios is a bid to force them back to the negotiating table with striking writers, guild leaders said.

But a studio alliance responded with disdain to the claim it illegally broke off talks, as alleged in Thursday's filing by the Writers Guild of America with the National Labor Relations Board.

The "baseless, desperate NLRB complaint is just the latest indication that the WGA's negotiating strategy has achieved nothing for working writers," the Alliance of Motion Picture and Television Producers said in a statement.

Negotiations in the six-week strike collapsed Dec. 7 when the alliance refused to bargain further unless the union dropped proposals that included the authority to unionize writers on reality shows and animation projects.

The labor board did not immediately return a call to its Los Angeles office.

It's not unusual for opposing sides in a labor dispute to file such complaints in an attempt to turn up the bargaining pressure, said Daniel J.B. Mitchell, a professor of management and public policy at the University of California, Los Angeles.

The guild said it expects the labor board to assign an investigator and complete an inquiry within 30 days.

Generally, if the board decides a complaint has merit, it can require a hearing that could lead to an order to resume bargaining in good faith or punitive measures such as fines.

"We find it outrageous that the AMPTP would walk out of negotiations in a holiday season while thousands are out of work," said Jeff Hermanson, assistant executive director of the Writers Guild of America, West.

A Dec. 7 letter to the guild from chief alliance negotiator Nick Counter insisting that a half-dozen proposals be dropped is "the smoking gun" proving the alliance violated federal law, Hermanson said Thursday.

Jonathan Handel, an entertainment attorney with the TroyGould firm and former associate counsel for the writers guild, said the union has made an "ill-considered and inflammatory" move that jeopardizes back-channel efforts to restart talks.

"The AMPTP would not want to look like it's caving into a legal threat," Handel said.

The complaint was filed the same day the Directors Guild of America said it may open its own contract negotiations with studios next month, a move that's expected to put more pressure on writers to reach an agreement.

A quick deal by directors could undercut the bargaining power of writers by serving as an industry template for new media and other issues.

Both sides in the writers strike have said the central issue is compensation for programs, movies and other content streamed or downloaded over the Internet.

That issue is also expected to dominate upcoming studio negotiations with directors and actors. The contracts of both those guilds expire in June.

The studio alliance said it looked forward to talking with directors but cautioned it would be "an extremely difficult process" because of the complexity of the rapidly changing new-media marketplace.

The directors guild represents about 13,500 directors and associated production workers.

Writers union sentiment so far contrasts sharply with the previous strike in 1988 that lasted 22 weeks, said Ross Brown, a longtime member of both the writers and directors guilds and an assistant professor at Chapman University's Dodge College of Film and Media Arts.

"Nobody likes the fact that there's a strike. But I heard open complaining in 1988 about the strike, and there were meetings of open dissent," he said. "I haven't heard a peep about that this time."

In New York on Thursday, a writers guild picket line outside media giant Viacom drew hundreds of guild members and supporters despite freezing cold, said Sherry Goldman, spokeswoman for the Writers Guild of America, East.