General Motors Corp's auditors have raised "substantial doubt" about the troubled automaker's ability to continue operations.

The company revealed the concerns, raised by the accounting firm Deloitte & Touche LLP, in its annual report filed yesterday.

GM has received $13.4 billion in federal loans as it tries to survive the worst auto sales climate in 27 years. It is seeking a total of $30 billion from the government. During the past three years it has piled up $82 billion in losses, including $30.9 billion in 2008.