Borussia Dortmund CEO Hans-Joachim Watzke has voiced fears that rules governing the ownership of German clubs could change, telling Sport Bild: "I don't want the fans to be milked as is happening in England."
The Bundesliga success of RB Leipzig, funded by Austrian soft drink company Red Bull, has sparked debate about the future direction of German clubs.
Although Leipzig formally abide by the 50+1 rule which stipulates that more than 50 percent of a club must be owned by its members, the influence of fans and other investors is limited.
With company-owned clubs, such as Bayer Leverkusen and Wolfsburg, and clubs bankrolled by wealthy individuals, such as Hamburg and Hoffenheim, the demise of the 50+1 rule no longer seems unthinkable.
"The 50+1 rule does significantly more good in Germany than harm," Watzke said.
He warned that investors unchecked by the rule would not necessarily be a good thing, adding: "Most clubs won't get a Roman Abramovich, who in the first place wants to see Chelsea winning.
"Most of the investors want to earn money. And where do they get it from? The spectators.
"The German spectator traditionally has close ties with his club. And if he gets the feeling that he's no longer regarded as a fan but instead as a customer, we'll have a problem."
Watzke said he believed an investor without checks on their plans could turn Dortmund's famous Sudtribune terrace into seating.
"An investor in Dortmund would soon turn 28,000 standing places into 15,000 seats, which would guarantee several million euros more per year," he added.
"But I don't want the fans to be milked as is happening in England."