Jean-Claude Trichet, the president of the European Central Bank, said on Friday that the complicated nature of many structured products had led to an over-reliance on credit ratings.

"The growing complexity of instruments has clearly induced some investors to overly rely on ratings," Trichet said. "This is the more risky as ratings in structured finance are not yet as much tested as those of corporate issuers. Some investors may also have misinterpreted the risk dimensions covered by a rating."