Lawrence Lasser is stepping down as chief executive of Putnam Investments in the wake of civil fraud allegations against the company and decisions by several big U.S. state pension funds to take money out of the firm’s funds.

Putnam’s parent company, Marsh & McLennan Companies Inc., announced Monday the departure Lasser, who over the last 18 years helped build Putnam into the fifth-largest mutual fund company in the United States.

Charles Haldeman, senior managing director and co-head of investments at Putnam, was named the new chief executive.

The announcement came one week after U.S. federal and state regulators filed civil fraud complaints against Putnam and two former portfolio managers.

Public pension funds in six states — Massachusetts, New York, Vermont, Pennsylvania, Rhode Island and Iowa — pulled more than $4 billion from Putnam last week.