New York Attorney General Eliot Spitzer, the scourge of Wall Street, may have found new prey: insurance brokers.

At least two big insurance brokers, Aon ( AOC) and Marsh & McLennan ( MMC), confirmed receiving subpoenas from Spitzer's office seeking information about the compensation insurers pay insurance brokers.

Willis Group ( WSH), a large insurance brokerage firm, said Friday that it, too, had received a similar subpoena.

Meanwhile, another half-dozen insurers also may have received subpoenas, a source says. The inquiry by Spitzer's office is said to be in its infancy and involves allegations of possible kickbacks to the insurers.

A Spitzer spokeswoman declined to comment on the office's newest investigation.

Spitzer's office has a lot on its plate right now with the investigation into abusive trading in the $7.6 trillion mutual fund industry far from over. The New York prosecutor is also looking into allegations of improper trading in variable annuities, a staple insurance industry product.

News of the insurance broker investigation emerged late Thursday when Chicago-based Aon issued a press release confirming that it had received a subpoena from Spitzer's office.

In the release, Aon said, Spitzer's office is "seeking information regarding certain compensation agreements between insurance brokers and insurance companies." The insurer also said "compensation agreements between insurance companies and brokers are a longstanding and common practice" within the industry.

Aon, in its annual report, says the firm receives "compensation from insurance and reinsurance companies with whom we place business for services provided to them.''

Earlier this year, the Washington Legal Foundation, non-profit public interest group, urged state officials in New York and California to investigate compensation deals in the insurance industry. In a February press release, the foundation said compensation deals can create a conflict-of-interest between and lead insurance brokers to do what's best for them and not necessarily in their client's interest.

"Insurance brokers are paid to advocate for their customers, not themselves,'' Daniel Popeo, the foundation's chairman, said at the time.

Two years ago, Spitzer became a household name when he upstaged the Securities and Exchange Commission by taking on Wall Street over the issue of conflicts-of-interest between investment bankers and stock analysts. The investigation started by Spitzer culminated with an industrywide $1.4 billion settlement over allegations that Wall Street analysts routinely hyped stocks of companies in order to secure investment banking work.

Last year, Spitzer trumped the SEC again when he announced in September that his office had found widespread improper trading in shares of mutual funds by hedge funds and other wealthy investors. The mutual fund investigation, which the SEC has since joined, has already led to mutual fund companies paying nearly $2 billion in fines and fee reductions.