NEW YORK (Bloomberg) ? Marsh & McLennan Cos., the world?s largest insurance broker, and dozens of insurers were accused of rigging bids in a lawsuit brought by policyholders including Tyson Foods Inc.

The suit, filed in US District Court in Atlanta on April 4, seeks unspecified damages and accuses the insurers of racketeering, conspiracy, fraudulent concealment, deceptive business practices and violations of antitrust law.

?The net result of these practices is that competition for policyholders? business did not occur,? the suit said. ?Policyholders including plaintiffs in turn either paid more for insurance products or received less beneficial terms than the competitive non-rigged market would have charged.?

The lawsuit says Marsh & McLennan rigged bids and steered business to insurers that paid it kickbacks, mirroring allegations made by New York Attorney General Eliot Spitzer in a 2004 suit. The New York-based company agreed in January 2005 to pay $850 million in restitution to clients who might have been overcharged, without admitting or denying any wrongdoing.

Aon Corp., Marsh & McLennan?s smaller rival, also is named in the suit, which says American International Group Inc., Ace Ltd., Zurich Financial Services AG and other insurers ?colluded with the broker defendants to rig bids and submit false quotes to unwitting clients?.

Patrick Heneghan, an attorney representing the plaintiffs, declined to comment. Marsh & McLennan spokeswoman Barbara Perlmutter, Aon spokesman Al Orendorff, AIG spokesman Chris Winans, Zurich spokesman Keith Owens and Ace spokesman Robert Grieves also declined to comment.

Shares of Marsh & McLennan fell 15 cents to $29.35 today in New York Stock Exchange composite trading. Tyson, based in Springdale, Arkansas, is the largest U.S. meatpacker.

The case is New Cingular Wireless Headquarters LLC v. Marsh & McLennan, No. 06CV796, U.S. District Court, Northern District of Georgia (Atlanta).