General Motors on Monday warned that Delphi, its biggest parts supplier, may not be able to emerge from bankruptcy protection. In a regulatory filing, the ailing US carmaker also painted a dark picture of prospects for ResCap, one of the US’s biggest mortgage lenders, controlled by GMAC, GM’s 49 per cent-owned financing unit.

The comments came on another bad day for GM, which lost a quarter of its market value after several analysts further ratcheted down projections of the ailing carmaker’s financial performance.