NEW YORK (Bloomberg) - Marsh & McLennan Cos. CEO Brian Duperreault won the support of investor KJ Harrison & Partners Inc., which rescinded a request for the insurance broker to spin-off security and human-resources units.

KJ Harrison had called in November for a break-up to boost Marsh & McLennan's stock, which lagged behind No.2 Aon Corp. under Mr. Duperreault's predecessor, Michael Cherkasky.

"We believe shareholders will be best served by supporting Mr. Duperreault," said Jim Harrison, CEO of the Toronto-based investment firm, in a statement on Friday.

Mr. Harrison said he backs Mr. Duperreault "in assessing which businesses Marsh & McLennan should continue to own and operate".

KJ Harrison owned 1.08 million shares in the New York-based company, or about 0.2 percent of its stock, at the end of 2007, according to Bloomberg data. Margaret Franklin, a KJ Harrison spokeswoman, said she could not say the current size of the stake.

Marsh & McLennan fell 82 cents, or 3.3 percent, to $24.29 at 4.15pm in New York Stock Exchange composite trading on Thursday. The company has a market value of about $12.7 billion.

Mr. Duperreault has said he plans to boost performance at each of the company's units, which include the Marsh Inc. brokerage, Kroll, Mercer human resources and Oliver Wyman consulting.

The executive was CEO of Ace Ltd., a Bermuda-based business insurer, from 1994 to 2004 as the company increased more than fivefold in New York trading.

"We are pleased Mr. Harrison has chosen to take this action," Marsh & McLennan spokeswoman Christine Walton said in an e-mail.

Mr. Cherkasky, a former prosecutor who cleaned up relations with regulators, failed to stop client defections amid the fallout from a 2004 investigation into bid-rigging by Eliot Spitzer, then the attorney general of New York.

Mr. Cherkasky reached an $850 million settlement, and the company neither admitted nor denied wrongdoing.

From Mr. Cherkasky's appointment on October 25, 2004, to December 20, 2007, the day before he said he would step down, the company lost about six percent. Aon, based in Chicago, gained 145 percent in that span.

• Mr. Duperreault, hired in January to restore profit lost after a 2004 bid-rigging scandal, is also shaking up management and last week promoted Ben Allen to head the company's Kroll security subsidiary.

In his new role, Mr. Allen succeeds Simon Freakley, who will serve as CEO of a newly-formed Marsh & McLennan Cos. (MMC) corporate advisory and restructuring unit.

"As one of the world's top risk consultants, we require strong leadership across MMC," Mr. Duperreault, said. "As our clients increasingly rely on a combination of technology and consulting to help them assess and mitigate risk, Ben is the ideal executive to oversee Kroll.

"I am also pleased that Simon has agreed to lead corporate advisory and restructuring as a separate consulting business at MMC. This structure gives greater clarity to our organisation and will allow us to serve clients more effectively."

Mr. Allen said: "I consider it an honour to serve as CEO of Kroll at this important time. Our clients face new challenges every day and must be able to assess and manage risks to their business quickly.

"Kroll's unique combination of best-in-class consulting, technology-enabled solutions and global reach allows us to create customised solutions to help clients respond to and mitigate risks that arise from conducting business in a complex environment."

Both Mr. Allen and Mr. Freakley will report to Mr. Duperreault.