General Motors Corp said on Thursday it expects auditors to cast doubt on the automaker's ability to remain viable as it endures the worst market in decades.

GM posted a deeper-than-expected quarterly loss as revenue plunged by more than a third. The automaker also warned its pension plans for hourly and salaried workers were underfunded by about $12.4 billion as of the end of 2008.

GM said it could receive a going concern notice from auditors, who will assess the risk that the automaker might not be able to continue as a going concern.

The company, which has been kept afloat with emergency loans from the U.S. government since the start of the year, posted a net loss of $30.9 billion for 2008.

That ranked as the second largest annual loss for the 100-year-old automaker on record behind only the $38.7 billion loss recorded for 2007.

(Reporting by Kevin Krolicki and David Bailey; Editing by Derek Caney)