The survey, carried out by the Federal Insurance Office (BVA) and seen by the Bild newspaper, contained several other examples of what it called "gross inefficiency" in the health insurance system.
One insurer rented out 4,700 square metres of office space for ten years at a cost of €96,000 per month - plus an extra €97,500 to install special facilities and furnish the office. It was then found to be only using 40 of the 117 desks, notching up a loss of €13 million.
The BVA also found that insurers were using their members' contributions to hold parties, complete with catering and entertainment, which contravenes government regulations.
The report even revealed one case of massive fraud, which it said the insurance company itself should have noticed long ago - an employee reportedly transferred a total of €459,000 to her private account - spreading 213 transactions over eight years.
The financial situation of many insurers is currently very good. The most recent figures show the country's insurance firms collecting €184 billion in 2011, and spending €180 billion.
The BVA has now demanded better internal control systems, but it also underlined that the inefficiency was not systematic. "They are isolated cases," a spokesman said in Der Spiegel magazine.