Willis has agreed to pay $50m into a restitution fund to settle US investigations into its business practices.
The agreement comes hot on the heels of similar settlements from Marsh and Aon.
The broker will pay $50m back to clients who were unfairly charged contingent commissions.
The investigations have uncovered market abuses in its wholesale arm and reinsurance tying and steering.
In 2003 Willis devised a centralised approach, designed to consolidate its negotiating strength with insurers and strike contingent commission arrangements based on profit or volume over-riders.
According to Spitzer, Willis also used its wholesale arm Stewart Smith “thereby gaining a second commission when Willis could have directly placed the business for a single price”.
Under the settlement, Willis has until 31 July 2005 to calculate a formula to compensate its US policyholder clients whose business was included in “contingent commissions or overrides recorded by Willis between 1 January, 2001 through 31 December, 2004”.