No 1 global broker Marsh will begin charging US insurers an "enhanced" commission for small and middle-market commercial business from early next year, CEO Michael Cherkasky has announced.

Marsh already charges a 2.5% brokerage fee on UK business and intends to replicate the practice in the US.

Mr Cherkasky says the decision to reinstate commission, which has not been charged by Marsh since 2004, was due to a market imbalance in the small commercial and middle-market segments where it competes with smaller brokers that accept contingent commissions.

The extra commission will be fixed and not be contingent on volume, profitability or other factors and will not be paid on large account business.

Mr Cherkasky says a few insurers have agreed in principle with the proposal to charge enhanced commission, and are likely to begin paying fees early next year.

The decision was revealed during parent company Marsh & McLennan's third quarter earnings announcement where the company reported a 40% drop in profit from continuing operations to $US80 million ($88 million).

Mr Cherkasky says the results were significantly impacted by the "unacceptable financial performance" of the insurance broking business.