WASHINGTON - The Obama administration's embattled mortgage-relief plan has provided permanent help to only 4 percent of borrowers who have signed up, weak results that could threaten the housing market's recovery.

Among big lenders, Bank of America Corp. had the worst performance in the Treasury Department report card released yesterday. The nation's largest lender completed just 98 modifications for the 160,000 borrowers who had signed up by the end of November. GMAC Mortgage had the most modifications of any lender, just 7,100.

As of last month, just over 31,000 homeowners had received permanent loan modifications. That compares with about 760,000 who have signed up for the program since it launched in March.

The report shows that the administration is not going to hit its long-term target of helping up to 4 million borrowers with modified loans, said Ted Gayer, an economist at the Brookings Institution.

The more borrowers that the program can't reach, the more foreclosed homes will spill onto the market, pulling down home prices. Almost 14 percent of homeowners with a mortgage are either behind or in foreclosure.

"Nobody really knows how big that wave will be," Gayer said.

The Treasury Department said that it will step up pressure on the industry to improve. The administration's focus is to "get as many of those eligible homeowners as possible into permanent modifications," said Phyllis Caldwell, chief of Treasury's homeownership preservation office.

Under the program, eligible borrowers who are behind or at risk of default can have their mortgage-interest rate reduced to as low as 2 percent for five years. They are given temporary modifications, which are supposed to become permanent after borrowers make three payments on time and complete the required paperwork, including proof of income and a financial hardship letter.

Lenders blame the low success rate on borrowers who don't return the necessary paperwork to complete the process.