An insurance consumer rights group, which started in New York but is now based in San Francisco, is suing the three largest global brokers, alleging they defrauded Californian customers by not disclosing the contingent commissions they received from insurers.

The lawsuits against Marsh, Aon and Willis have been filed by United Policyholders.

This is the latest development in a growing controversy in the US, with regulators in New York and California investigating the top three brokers for possible conflicts of interest for taking commissions from insurers while charging clients fees.