Fannie Mae, the mortgage-finance company taken over by the U.S. government this month, said bankrupt securities firm Lehman Brothers Holdings Inc. owes it "very substantial sums."

The exact amounts "change on a nearly daily basis," Fannie said in a filing today with the U.S. Bankruptcy Court of the Southern District of New York. Lehman was one of the company's frequent business partners in servicing home loans and the mortgage bonds Fannie and fellow government-sponsored enterprise Freddie Mac guarantee. Lehman executed a $5 billion repurchase agreement with Washington-based Fannie in the first quarter, company filings show. Brian Faith, a spokesman for Fannie, declined to comment. McLean, Virginia-based Freddie said this week that Lehman owes it at least $1.6 billion in loans and repurchase agreements. About $1.2 billion is related to unsecured lending transactions that were due to be paid in full, with interest, on Sept. 15 of this year, Freddie said in a statement today. New York-based Lehman also owes Freddie $400 million in repurchase agreements and servicing-related fees. Freddie said it hasn't received any payments yet and that "actual losses could materially exceed current estimates."

Conservatorship

Lehman, which listed $613 billion in debt and $639 billion of assets in its bankruptcy filing, was once one of the biggest underwriters of mortgage-backed securities. Lehman filed the largest bankruptcy in history this week after succumbing to losses stemming from subprime mortgage bonds.

Federal regulators on Sept. 7 placed Fannie and Freddie into a so-called conservatorship and ousted their boards and chief executive officers amid concern that the companies might not survive the worst housing slump since the Great Depression because of potential losses in their portfolios. Fannie and Freddie make money by buying mortgages from banks and by guaranteeing home-loan securities. The companies also hold some loans and mortgage bonds in their portfolios as investments. Fannie's Chief Business Officer Peter Niculescu,

General Counsel Beth Wilkinson, Chief Information Officer Rahul Merchant and Duane Duncan, who ran the company's lobbying operations, all resigned today, the company announced.