Jeffrey Greenberg, chief executive and chairman of Marsh & McLennan, the US broker, has resigned. His departure follows accusations by Eliot Spitzer, the New York state attorney general that the world's largest insurance group has been rigging prices.

Greenberg will be replaced by Michael Cherkasky. Two weeks ago he was appointed head of Marsh, the firm's risk and insurance business and before that was in charge of Kroll, the risk consultancy now owned by Marsh and McLennan.