Deutsche Bank, Germany’s biggest banking group, said yesterday it has uncovered four incidents of “questionable investigative or surveillance activities” at the firm, dating back as far as 1998, but there was no sign that current management board members were involved or knew what had happened.

The findings were published in a report that was issued after checks by law firm Cleary Gottlieb Steen & Hamilton in Frankfurt, carried out on Deutsche’s behalf.

The statement by Deutsche did not specify whether the incidents affected wealth management operations at the firm, however.

Among the principal findings were that four incidents that raise legal issues such as data protection or privacy concerns were identified; in all incidents, the activities arose out of certain mandates performed by external service providers on behalf of the bank's corporate security department and the incidents were isolated.

“Deutsche Bank has informed all persons affected by the aforementioned activities (with the exception of the private individual whose whereabouts are unknown) and expressed its sincere regrets,” the bank said.

The bank has also sacked the head of corporate security for Germany and the global head of investor relations, who were involved in the incidents, it said.