GMAC was formerly the finance arm of carmaker General Motors
The US finance group GMAC has failed to raise enough capital to cover potential losses and will need further government aid, the Federal Reserve has said.
The firm, formerly the finance arm of General Motors, was one of 10 US banks told to raise extra funds by the Fed.
In May, the Fed ordered the banks to come up with $74.6bn (£44.5m) of extra funds to boost their cash reserves.
The order came after the government's "stress tests" determined whether banks could cope if the recession worsened.
Nine of the 10 succeeded in raising the required additional capital.
"The one exception, GMAC, is expected to meet its remaining buffer need by accessing the Troubled Asset Relief Programme (TARP) Automotive Industry Financing Program, and is in discussions with the Treasury on the structure of its investment," the Fed said.
GMAC has received billions of dollars of government aid to combat mortgage losses and to provide funds for Americans to buy cars.
In December last year, the government stepped in with a $6bn bail-out.
In May this year, the Treasury announced that it would provide a further $7.5bn in aid.
In 2006 GMAC became an independent finance company after GM sold a 51% stake in the business.
In May of this year, GM further reduced its stake in the company.
The nine banks that managed to raise enough capital are Bank of America, Wells Fargo, Citigroup, Morgan Stanley, Regions Financial, SunTrust Banks, KeyCorp, Fifth Third Bancorp and PNC Financial.
Nineteen banks were originally stress-tested.
Those that did not require extra funds were Goldman Sachs, JPMorgan Chase, Bank of New York Mellon, MetLife, American Express, State Street, BB&T, US Bancorp and Capital One Financial.