(Bloomberg) ? Two underwriters at Zurich Financial Services AG, the third-biggest US commercial insurer, pleaded guilty to charges they helped rig bids to help an insurance broker give business to favoured clients.

The two men, John Keenan and Edward Coughlin, worked exclusively with Marsh & McLennan Cos., according to plea agreements at their arraignment yesterday in New York State Supreme Court.

The pleas bring to five the number of people who have admitted roles in the illegal business practices under investigation by New York Attorney General Eliot Spitzer.

"The investigation is proceeding carefully and methodically," Spitzer said in a statement. "Our goal is to determine the full extent of wrongdoing in the industry and its effect on consumers."

More than 17 people have been forced out or suspended since Spitzer sued Marsh, the world's largest insurance broker, on October 14.

Marsh Chief Executive Jeffrey Greenberg was forced to resign after Spitzer refused to negotiate with him. Two executives from American International Group Inc. and one from ACE Ltd. pleaded guilty last month.

Keenan and Coughlin each pleaded guilty to a misdemeanour under New York State's Donnelly Act, which bars agreements in restraint of trade. They face a maximum sentence of one year in state prison.

The two employees no longer work at the company, said Zurich spokesman Keith Owens. Keenan and Coughlin were part of an unspecified number of employees in the excess-casualty unit suspended last week, Owens said.

In his complaint against Marsh, Spitzer said insurers inflated quotes as part of a phony bidding system Marsh designed to steer business to the insurers that paid it the highest fees.

Spitzer and other state officials told a US Senate panel yesterday that alleged abuses they found in the insurance industry indicate the need for more federal oversight, including tougher antitrust rules. Keenan and Coughlin, who worked exclusively with Marsh Global Broking between 2002 and 2004, are expected to testify in future cases, Spitzer's office said.

"I don't think the attorney general's office is going to bring any of these cases to trial," said Lewis Weiner, an attorney for Coughlin.

"They're squeezing these low-level people and that's not right."