The investigation into the behaviour of US financial advisers in relation to flotations on Wall Street has widened into a "Street sweep" of nearly all big firms.

Sources in the financial community say that at least two other firms, Lehman Brothers and UBS Warburg, have received subpoenas from the US Securities and Exchange Commission (SEC) in addition to those reported previously - Credit Suisse First Boston (CSFB), Goldman Sachs, Morgan Stanley Dean Witter and Bear Stearns.

Thus far, it is believed that only CSFB has received subpoenas from more than one governmental agency, thought to include the office of the US attorney in the Justice Department.

Regulators are investigating whether firms that underwrote some of the best performing IPOs in the past two years used illegal means in their allocation of shares to their customers.