Two of the four banks giving evidence before the UK's Treasury Select Committee this morning admitted selling complex structured debt products to investors that "did not fully understand what they were buying", as the parliamentary group continues its investigation into the causes and effects of the credit crisis.

The admissions came amid a parliamentary grilling into the crisis that has engulfed lender Northern Rock. Last month the UK's powerful Treasury Select Committee said it would broaden the scope of its probe to analyse the participation of investment banks, hedge funds, credit ratings agencies and other participants of the financial markets in the events leading up to a run on the bank in September.