A German newspaper report has revealed major historical ties between the Reimann family, owners of Krispy Kreme and Pret a Manger, and the Nazi party.

The report in Bild, since confirmed by the family’s spokesman, shows that ancestors of Reimann family were enthusiastic antisemites and keen supporters of Adolf Hitler. They used Russian civilians and French prisoners of war as forced labourers in their factories.

The report contains harrowing details about the family’s treatment of forced workers: female slaves, mostly from eastern Europe, were forced to stand naked in the factory barracks during checks. Those who refused were beaten and sexually abused. Other workers were beaten, often by the Reimanns themselves, including a Russian woman who worked in the Reimanns’ private villa.

In July 1937, Albert Reimann Jr wrote to Heinrich Himmler, the SS leader responsible for the Holocaust, saying that his business was “a purely Aryan family business that is over 100 years old”, he wrote. “The owners are unconditional followers of the race theory.”

After Hitler came to power, millions of ethnic Slavs were forced to work in Nazi factories or in German agriculture for no payment. The Reimanns’ enthusiastic support for the Nazis’ racial ideology and personal abuse of workers is uniquely shocking.

Reimann Jr amassed a huge fortune which was passed, through shares in his company, to his nine adopted children, four of whom now control the company. The Reimann family are now the second richest family in Germany with an estimated net worth of €33bn ($37bin). Through JAB Holding, a private company owned by the family, they also have majority shares in Peets Tea and Coffee, Panera Bread and Dr Pepper.

The source of the revelations appears to be a report commissioned by the family themselves, in an effort to learn more about their ancestry. After discovering the extent of the Nazi ties, the family have said they will donate $11.3m (£8.5m) to charity, though they are yet to say which one.