NEW YORK (Bloomberg) - Marsh & McLennan Cos., the world's largest insurance brokerage, will seek to sell parts of its Kroll security unit after a $425 million writedown at the subsidiary caused a first-quarter loss.

"There are businesses in Kroll that do not necessarily fit," CEO Brian Duperreault said in a conference call yesterday. "We will seek ways to divest these businesses."

Marsh & McLennan has been pressured by investors to spin off Kroll, which conducts investigations and sells security advice, because they say the unit isn't a good match with the parent company's insurance brokerage and consulting businesses. The company rejected an approach from a private equity firm interested in buying Kroll, a person familiar with the situation said May 1.

Marsh & McLennan posted a net loss of $210 million, or 40 cents a share, on the Kroll impairment, the company said yesterday in a statement.

The New York-based company earned $268 million, or 47 cents, in the same period a year earlier. Mr. Duperreault, hired in January to restore profit lost after a 2004 bid-rigging scandal, said some parts of Kroll were "underperforming".

The charge is "a positive recognition of the reality of Kroll right now," said Cliff Gallant, an analyst at KBW Inc. "Cleaning it up and separating it may better position him to sell portions of Kroll."

Kroll, purchased by Marsh & McLennan in 2004 for about $1.93 billion, serves companies, government agencies, law firms and individuals in more than 30 countries. It employs about 4,800 people.

Parts of Kroll that provide services to mortgage lenders and some government agencies "may have greater value outside" Marsh & McLennan, Mr. Duperreault said yesterday. Those businesses "drove the impairment charge".

Kroll's adjusted operating profit, excluding the impairment charge, fell 31 percent to $18 million. The unit's adjusted profit margin of 6.9 percent was the lowest of Marsh & McLennan's three operating divisions.

Marsh & McLennan gained five cents to $27.63 at 9.33am in New York Stock Exchange composite trading. The firm has declined about 13 percent in the last year, compared with the 13 percent gain in No.2 brokerage Aon Corp. and the 14 percent decline in No.3 broker Willis Group Holdings Ltd.