LONDON (AP) - Shares in commodities group Glencore PLC have slumped by a fifth after an investment bank warned that the company faced a bleak future if commodity prices don't recover.

LONDON (AP) Shares in commodities group Glencore PLC have slumped by a fifth after an investment bank warned that the company faced a bleak future if commodity prices don't recover.

In a note to clients Monday, Investec Securities said mining companies "gorged themselves on cheap debt" in a race to grow production following the Chinese stimulus in the wake of the global financial crisis and that the consequences are "only now coming home to roost, as mines take a long time to build."

As a result, the bank said Glencore could see all its equity value "evaporate" if major commodity prices stay at current levels. Investec said Anglo American Group PLC faced a similarly bleak outlook.

Glencore's share price was down 20 percent at a record low of 77 pence ($1.17).