Düsseldorf state prosecutors are investigating seven former and current board members of WestLB in connection with massive trading losses racked up at the German state-owned bank earlier this year.

The bank’s former chief executive, Thomas Fischer, who stood down from WestLB last month in the wake of the trading scandal, is among those being investigated, prosecutors said.

Mr Fischer's departure from WestLB followed an extraordinary supervisory board meeting, called to investigate whether the bank’s management board acted improperly in failing to report on positions taken by its proprietary equities trading business.

Mr Fischer also chairs the non-executive supervisory board of RWE, the German utility group.

The six other suspects in the Düsseldorf state inquiry were not named.

WestLB has so far admitted to trading losses of at least €243 million (£164 million) from suspect share trading in the first half. There is speculation that the deficit could have hit more than €500 million, though later trading gains could have reduced that figure.

Prosecutors are investigating allegations that the managers failed to keep the supervisory board informed of the bank’s activities.

WestLB declined to comment to Reuters. A spokesman for Mr Fischer was not immediately available.

The bank made the losses on trading in common and preference shares of several major German companies earlier this year.

Mr Fischer stepped down after Germany’s financial regulator said the bank’s supervisory board had not been properly informed about the matter.

BaFin, the German securities watchdog, has also launched an investigation after WestLB initiated criminal proceedings against a former management board member and a former managing director in connection with the trading losses.

WestLB traders are alleged to have manipulated share prices in a number of companies, including BMW and Volkswagen, to inflate the bank’s trading profits and boost their own bonuses.

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