NEW YORK—Guy Carpenter & Co. Inc. is suing three former top London-based officials over their resignations last month to join Integro Insurance Brokers Ltd.

The suit, filed late last week in U.S. District Court in New York, does not seek to enforce noncompete agreements; instead, it charges that the three violated terms of a Marsh & McLennan Cos. Inc. incentive bonus plan, and it seeks repayment of about $370,000 in vested awards.

Named in Guy Carpenter's complaint are Julian Samengo-Turner and Ron Whyte, former co-leaders of the Marsh unit's global facultative reinsurance operation in London; and Marcus Hopkins, former head of Guy Carpenter's U.K. facultative unit.

All three resigned from Guy Carpenter on April 3. Two days later, Integro announced it had hired them to form a new London insurance and reinsurance brokerage operation.

According to the suit, Messrs. Samengo-Turner, Whyte and Hopkins participated in a Marsh senior executive incentive and stock award plan. The plan's terms included a "cooperation clause," which requires them to answer questions about their work for Guy Carpenter "or other commercial activities."

After their resignations, Guy Carpenter sought answers to questions that included the circumstances of their hiring by Integro and the details of discussions they had with Guy Carpenter employees about their hiring. The three have not responded to the queries, the suit says.

The Marsh incentive plan also allows for rescission for "detrimental activity" by an executive, including encouraging other employees to leave the company. Guy Carpenter charges that the three men aided Integro in soliciting at least eight other Guy Carpenter employees to join rival Integro.

The suit seeks an order enforcing the cooperation clause and requiring the three to forfeit incentive awards paid since April 2006. For Mr. Samengo-Turner, that would amount to about $154,000; for Mr. Whyte, about $123,000; and for Mr. Hopkins, about $92,000, according to the complaint.

None of the three men could be reached, and Integro declined to comment.