NEW YORK (Bloomberg) ? Aon Corp., the world?s second-largest insurance broker, sued startup competitor Integro Ltd., accusing it of a ?campaign to pirate? Aon employees.

Integro has hired 15 Aon employees since August, starting with Gary Marchitello, the former head of Aon?s national property practice, the complaint says.

The suit accuses one former Aon executive, David Finnis, of being a key figure in the recruiting, and says he violated an Aon employment contract that barred him for two years from soliciting his colleagues to take other jobs.

The 19-page complaint was filed by Aon?s Georgia unit on February 13 in Fulton County Superior Court in Atlanta, where Aon said it lost four of its five-member property-insurance team to Integro.

Gaye Torrance, a spokeswoman for Integro, and Al Orendorff, an Aon spokesman, both declined to comment on the suit.

Integro, based in New York, was started last May by former executives of number one insurance broker Marsh & McLennan Cos. after New York Attorney General Eliot Spitzer accused the top three brokerage firms of taking kickbacks from insurers.

?Clients wants more choice,? Integro chief executive officer Roger Egan said at the time. Egan stepped down as president of Marsh?s brokerage unit after Spitzer?s suit and left the following April.

The three companies ? Chicago-based Aon, New York-based Marsh, and No. 3 Willis Group Holdings Ltd. of London ? together paid almost $1.1 billion last year to settle the charges.

Egan has said his target customers are the world?s largest companies and those with the most complex insurance needs. The three largest broker companies have usually dominated this market.

Egan has also said the company is engaged in an aggressive campaign to hire ?the best? brokers from Marsh, Aon, Willis and other companies.

He said in a January interview that about 40 percent of the 200 employees recruited so far were from Marsh, about 30 percent from Aon, and another 10 percent from Willis, roughly reflecting each company?s market share.

According to the lawsuit, Finnis came to Aon in 1996, rising to the position of director of national property syndication, with ?leadership responsibility? for Aon?s southeastern US operation. Finnis signed a four-year employment contract last April, the suit says, which included clauses barring him from trying to hire away colleagues for two years, should he take another job, and barring him from acting against Aon?s best interests while still at the company.

The suit says Finnis violated that agreement by ?directly or indirectly? recruiting Aon employees after he joined his former boss Marchitello at Integro in November 2005.

The complaint says Finnis also solicited Nashville, Tennessee-based HCA Inc., the largest US hospital chain, to switch its insurance-brokerage business to Integro before he left Aon. HCA made the switch in November, the lawsuit says, depriving Aon of ?one of [its biggest accounts?.

Integro and Marchitello are accused in the suit of inducing Finnis to breach his contract. The suit doesn?t say whether Marchitello had signed a similar employment agreement.

Aon is seeking an injunction blocking Finnis from soliciting any more Aon employees and unspecified damages.