"In concrete terms we've lost around 500 customers," Ergo boss Torsten Oletzky told the Rheinische Post newspaper.
Ergo hit the headlines earlier this year when it was revealed that its subsidiary Hamburg-Mannheimer had thrown a sex party with prostitutes for its sales reps in the historic Gellert health spa in Budapest, Hungary.
The company was then hit by news that thousands of customers' pensions contracts contained erroneous data.
Business daily Handelsblatt reported in June that at least 70,000 customers who signed up in 2005 and 2006 for Hamburg-Mannheimer's Kaiser-Rente programme – which were part of the company's Riester-Rente offerings – were charged markedly higher administrative fees than outlined in contracts.
The company may have wrongly raked in millions due to the widespread overcharging, the newspaper reported.
"We've just received an interim report from the auditors at PriceWaterhouseCoopers," Oletzky said on Saturday. "We're expecting a concluding report at the beginning of August."
The company has also been dogged by allegations of giving questionable advice in its accident insurance policies.
Ergo's parent company Munich Re has backed Oletzky as the right man to clean up the company's image, and has consistently said it would not sell the concern.