No 2 broker Aon Corporation is facing a class action lawsuit in the US which alleges it breached its fiduciary duty by taking contingent commissions from insurers without disclosing them to policyholders.

A county court in Chicago has ruled that a 1999 lawsuit on the controversial industry practice can go ahead as a nationwide class action against Chicago-based Aon and its subsidiaries Aon Group and Aon Services. 

New York Attorney-General Eliot Spitzer is investigating Aon and several other leading brokers on whether contingent commissions represent a conflict of interest.