Six months after fall of Bear Stearns, another Wall St giant falls. No federal bailout this time.

Lehman Brothers, one of Wall Street's oldest firms, has issued a statement saying it intends to file for protection under Chapter 11 of the US Bankruptcy Code.

The fall of Lehman comes six months after fellow investment bank Bear Stearns, the first big Wall Street victim of the credit crunch, was acquired by JPMorgan with federal assistance.

But this time the Treasury Department and Federal Reserve refused to commit taxpayer money to help Lehman. They had been severely criticised for helping the purchase of Bear Stearns. Their refusal to help this time appears to have prompted Barclays to withdraw from talks to acquire Lehman.

The collapse of Lehman is likely to send markets into turmoil. However, Lehman said customers of its brokerage arm and its Neuberger Berman asset management unit could continue to trade and otherwise access their accounts.