The WSJ has been told that David Aufhauser is the person described in the case against UBS as "Executive A".

Mr Aufhauser has not been named by the attorney-general and has not been charged with any wrongdoing. The WSJ notes also that he ultimately bought some securities back.

UBS is alleged to have sold clients into illiquid securities at the same time as executives within the firm were dumping holdings of the very same security. UBS has admitted it had found cases of “poor judgement by certain individuals” and that it was evaluating appropriate disciplinary measures in relation to the movement of auction rate securities inventory from the firm’s own books and into private client accounts.

The firm said it had conducted its own internal investigation with the assistance of external counsel on sales of personal holdings of ARS, but had not found cases of illegal conduct by any employee. “We will vigorously defend ourselves against this complaint,” UBS said in a statement.

The investigation comes at a time when a number of financial institutions, including Merrill Lynch, have been investigated over the sale of these debt instruments.

Late last month, media reports said that UBS has suspended David Shulman, head of its US fixed income unit, amid state and federal probes of sales of auction-rate securities. A spokesman for Mr Shulman, who was also UBS's global head of municipal securities, said he was cooperating fully with UBS as it works through the matter.

New York State Attorney General Andrew Cuomo has sued UBS, accusing it of committing a "multi-billion dollar fraud" by steering clients into auction-rate securities that became impossible to sell once the credit market tightened.

UBS has recently announced a plan to buy back as much as $3.5 billion in auction-rate securities from customers.