NEW YORK (Bloomberg) — GMAC LLC, bolstered by a $6 billion federal bailout, resumed lending to General Motors Corp. customers with lower credit scores as the US stepped up efforts to keep the automaker in business.

The US Treasury said it will take a $5 billion stake in Detroit-based GMAC, the financing arm of GM, and lend $1 billion to the automaker that will be invested in GMAC to boost its capital. Within hours, GM was offering five-year, no-interest loans to halt this year's 22-percent slide in sales, which dealers have blamed on a lack of financing for customers.

Reviving GM's sales has become a priority for US policy-makers including the Federal Reserve because of concern that the automaker and its suppliers might go bankrupt and deepen the year-old recession by firing millions of workers. The funds for GMAC are on top of $13.4 billion the Treasury agreed earlier this month to lend to GM and Chrysler LLC.

"The economy has stopped on a dime, and the Fed is looking anywhere there are large markets they can affect in big ways," said Greg Prost, chief investment officer at Ambassador Capital Management in Detroit, which manages about $800 million. "If they are going to save the car companies, there is going to have to be financing."

GMAC will now lend to vehicle buyers with credit scores of 621 or higher, compared with a previous standard of at least 700, according to a company statement. The higher threshold had excluded about 42 percent of US consumers.

The company said it won't finance "higher-risk transactions", instead concentrating on prime customers who are more likely to repay using "responsible credit standards". The relaxed policy "will allow us to return to more normal levels of financing volume, and should help in efforts to stabilise the US auto industry," GMAC President Bill Muir said in yesterday's statement.

The lender financed about 35 percent of GM's retail customers and about three-quarters of dealer inventory last year. GM, which sold 51 percent of GMAC in 2006 to a group led by private equity firm Cerberus Capital Management LP, is seeking a permanent federal bailout to avert bankruptcy. Cerberus also owns Chrysler.

"The relationship with GM is probably a key reason it's being bailed out," said Thomas Atteberry, who helps manage $3.5 billion in fixed-income assets at First Pacific Advisors in Los Angeles. "I'm not very happy about the fact that the government has to save an auto-finance company because management ran it into the ground."

GMAC ran short of cash this year after $7.9 billion of losses over five quarters, mostly from record defaults on sub-prime mortgages, which are made to homebuyers with the worst records. The lender was shut out of credit markets and had to limit lending only to people with the top repayment histories, a policy that GM dealers said had cut deeply into sales.

"Bringing back loans is going to help tremendously, certainly with the perception of GM's stability," Mike Deichmann, owner of Trent Cadillac-Buick-Pontiac-GMC in New Bern, North Carolina, said in an interview. "These are all positive steps to get people to buy again, to visit the showroom."

GMAC's eight-percent bonds due in 2031 jumped 6.75 cents to 54.75 cents on the dollar to yield 15.1 percent at 1.09 p.m. in New York, according to Trace, the Financial Industry Regulatory Authority¿s debt-pricing service. The bonds, which traded at a low of 25 cents on November 24, have jumped 21.75 cents since the Fed on December 24 said it had approved GMAC's bank holding company application. GM's stock rose five percent in New York Stock Exchange trading.