Marsh & McLennan Cos. has sued the former head of its Marsh USA office in Honolulu, saying he violated employment agreements when he moved to his insurance practice competitor Aon Corp. last month, allegedly taking clients with him.

The lawsuit filed in U.S. District Court alleges Chad W. Karasaki was prevented from joining Aon's Honolulu office as its chairman and chief executive officer because of the agreements. This included restrictions on him from working with Marsh's clients or prospects for a period of a year after he left the company.

The lawsuit said several of Marsh's current and prospective customers have informed them they are leaving Marsh for Aon.

Karasaki referred questions to his attorney, Jeff Portnoy, who said he couldn't respond because he had yet to see the lawsuit.

"We haven't seen it and we haven't been served," Portnoy said.

Marsh also alleged Karasaki had specialized knowledge in construction insurance, including something known as owner controlled insurance programs. Karasaki also was aware of Marsh's trade secrets along with strategic and tactical plans to compete with Aon in Hawai'i, according to the lawsuit's claims.

Besides joining Aon as head of its Hawai'i office last month, Karasaki also was appointed managing director of the Aon Construction Services Group.

The lawsuit is asking for an injunction against Karasaki, and for an order preventing him from performing or supervising insurance services for any ex-Marsh customer. It also asks for payment of damages to be determined by a court.