Aon, Marsh and Willis are under scrutiny by New York attorney general Eliot Spitzer about incentives offerred by underwriters.
It is understood that complaints surround the issue of brokers not selecting underwriters based on best value to the client.
Spitzer's office has subpoenaed the three biggest US insurance brokers, seeking information on a widespread form of payment from insurers to brokers.
The subpoenas were disclosed by Aon of Chicago, Marsh of New York, and Willis of New York. All three companies said they routinely disclose the fact that they enter such agreements, both to clients and publicly.
