Aug. 5 (Bloomberg) -- Fannie Mae, the largest U.S. mortgage- finance company, will raise a fee it charges lenders to buy their mortgages or guarantee home-loan securities, a move that may increase costs for borrowers.

Fannie Mae's ``adverse market delivery charge,'' introduced earlier this year for all mortgages that the company helps finance, will rise to 0.50 percentage point on Oct. 1, from 0.25 percentage point, according to a letter to lenders posted on the Washington-based company's Web site.

Government-chartered Fannie Mae and Freddie Mac have been tightening standards and raising fees since last year to boost revenue and limit losses amid the worst housing slump since the 1930s. The changes have made it harder or more expensive for borrowers to get home financing, contributing to deeper price drops, said consultant David Lykken of Mortgage Banking Solutions in Austin, Texas.

``Everyone has to go to Fannie Mae and Freddie Mac right now, as there are very few alternatives,'' Lykken said. The latest fee increase will ``increase loan prices and the housing market is going to get worse.''

Fannie Mae and Freddie Mac now finance about 70 percent of new U.S. home loans, according to analysts at Morgan Stanley. The U.S. Congress last month enacted an emergency-rescue plan for the companies put forward by Treasury Secretary Henry Paulson after a plunge in their share prices sparked a crisis in confidence. Stock analysts expect the companies to report net losses through the first quarter of 2009.

Cost Changes

In the Aug. 4 letter, Fannie Mae also said it adjusted what it will pay for, or charge in guarantee fees on, loans with certain down payments, borrower credit scores or combinations of the two. Costs will fall for some loans to consumers with scores greater than 620, out of a possible 850, and loan-to-value ratios of more than 85 percent, for which Fannie Mae requires borrowers to buy insurance that cover some of its foreclosure losses. They'll rise for some loans with down payments or home equity of between 15 percent and 25 percent.

``Fannie Mae is announcing these changes to better align pricing with credit risks, mitigate losses and support Fannie Mae's ability to provide a stable source of liquidity to lender partners,'' said Marilyn Kornfeld, a company spokeswoman.

The increase in rates on Fannie Mae loans from the various changes will range between 0.06 percentage point and 0.18 percentage point, according to a report today from Barclays Capital analysts Matthew Seltzer and Derek Chen. The average rate on a 30-year, fixed-rate mortgage rose to 6.35 percent yesterday, compared with 5.79 percent on Dec. 31, according to Bankrate.com.

Rising Delinquencies

Fannie Mae announced the adverse-market fee in December and put it into effect in March. McLean, Virginia-based Freddie Mac also began charging a similar 0.25 percentage point fee.

``We're always looking at our fees in light of market developments,'' Brad German, a Freddie Mac spokesman, said in a telephone interview today.

With Fannie Mae's new adverse-market fee, a lender selling a $300,000 mortgage to the company will forfeit $1,500, up from $750. The lender, which would typically make less than $3,000 on the sale, could get paid more to offset the charge by raising the interest rate on the loan.

Home prices in 20 of the largest U.S. metropolitan areas dropped 15.8 percent from a year earlier in May as the collapse of the market for mortgage bonds without guarantees from Fannie Mae, Freddie Mac or federal agency Ginnie Mae eliminated certain lending completely, according to an S&P/Case-Shiller index.

Tighter Qualification Standards

Fannie Mae, Freddie Mac, mortgage insurers such as Milwaukee, Wisconsin-based MGIC Investment Corp. and Philadelphia-based Radian Group Inc. and banks such as Seattle- based Washington Mutual Inc. and Charlotte, North Carolina-based Wachovia Corp. have also announced tighter qualification standards or higher costs for other loans.

Fannie Mae, which Congress created to expand homeownership and provide market stability, also has loosened some standards over the past year to combat the housing crisis and address critics.

In May, Fannie Mae said that it would scrap a rule that boosted down-payment requirements by 5 percent in areas with falling prices, in favor of across-the-country limits that eliminated the company's 100 percent financing programs completely. The change allowed down payments of as low as 3 percent on some loans even where prices are declining.

That month, the company also said that it will handle refinancings of non-delinquent mortgages for as much as 120 percent of property values when it owns the existing loans, and agreed to buy ``jumbo'' mortgages, or those bigger than $417,000, for the same prices as smaller loans.

Fannie Mae's Kornfeld said the company has now announced reduced fees on some loans because ``providing financing options for borrowers with modest down payments has long been a significant part of our core business and mission, and may help stimulate housing recovery in many communities.''

To contact the reporter on this story: Jody Shenn in New York at jshenn@bloomberg.net.

Last Updated: August 5, 2008 15:49 EDT