Merger guidelines need update - U.S. regulator

WASHINGTON Dec 3 (Reuters) - U.S. guidelines on how regulators assess mergers tell business too little about how antitrust agencies work and fail to take the latest economic theories into account, Federal Trade Commission Chairman Jon Leibowitz said on Thursday.

His remarks kicked off an effort to revamp guidelines, in place since 1992, for horizontal mergers -- or mergers of rivals.

The FTC and Justice Department, which share the work of giving deals a legal thumbs up or down, will co-host five conferences in advance of releasing new guidelines.

"From my perspective the current guidelines have worked pretty well," said Leibowitz. "Yet they don't explain the process clearly enough to businesses ... And they don't incorporate the latest economic thinking."

Neither Leibowitz nor Christine Varney, who heads the Justice Department's antitrust division, would comment on the biggest antitrust issue of the day: Comcast's (CMCSA.O) plan to buy a majority stake in NBC Universal from General Electric Co (GE.N).

The deal would give one company huge power in not only creating entertainment but also delivering it to consumers' homes.

The Obama administration took office earlier this year with antitrust experts predicting it would give corporate combinations a tougher review.

One sign could be the Justice Department's opposition to Google Inc's (GOOG.O) controversial deal with authors and publishers that would allow the search engine giant to create a massive online digital library.

The review of the merger guidelines, adopted in 1968 and revised in 1982 and 1992, comes as merger activity shows signs of recovering from the financial crisis.

Globally, deals worth $234 billion were announced in November, the second-busiest month in the past 12 months. The busiest month in the past year was June with $275 billion in deals announced. (Reporting by Diane Bartz; Editing by Tim Dobbyn) ((Diane.Bartz@ThomsonReuters.com; +1 202 898 8313))