Eliot Spitzer, the New York state Attorney General has issued subpoenas against Marsh & McLennan and Aon, the two largest insurance brokers in the world, as his campaign to clean up US capital markets moves to the insurance sector.

Marsh & McLennan, owner of Putnam Investments, the embattled fund management firm caught up in the improper mutual fund trading scandal in the US, said it was cooperating fully with the enquiries.