Bayern Munich president Uli Hoeness has said the Bundesliga would die if Bayern and Borussia Dortmund ever became part of a breakaway European League.
Speaking at an event in Vaduz, Lichtenstein, Hoeness said Germany's top division would "become a second-rate product" without the two powerhouse clubs, with interest dwindling.
He said Bayern had "distanced ourselves" from the idea of a European league because it would "inevitably lead to the Bundesliga dying."
Bayern CEO Karl-Heinz Rummenigge, also the chairman of the European Clubs Association, revealed last year that initial discussions about a European league had taken place.
But in March he stressed that there were no immediate plans for it to be set up and that Champions League reforms meant clubs were "totally happy under UEFA."
Hoeness said he believed that "some of the bigger clubs want a European league, especially in Spain, but a few in England too."
But he added: "Bayern doesn't want this. I don't know if it will still be like this in 20 or 30 years, but as long as we have a say in it, we will prevent it happening."
Hoeness also discussed last month's quarterfinal exit from the Champions League, which means Bayern will end the season with only the Bundesliga title to show for their efforts.
He added: "I've said in the long term that a single title is not enough. But essentially, the German championship is a fantastic title.
"Of course, we were unlucky to meet Real Madrid -- probably the best team around -- in the Champions League quarterfinals.
"However, I wouldn't say we need to hide from Real or Juventus. I think Juve, Real and Bayern are the three best teams in Europe at the moment, and that isn't likely to change for a while."
Hoeness said winning the Champions League meant dealing with astronomical players' salaries, a trend he described as "alarming to some extent."
"If it carries on like this other clubs -- not so well structured as us -- will make losses," he added.
"Of course, you could insist nobody earns more than €5m, but you cannot win the Champions League like that. [Lionel] Messi earns €5m a month."
The 1974 World Cup winner World Cup winner spoke about Bayern's progress to becoming a footballing superpower, recalling: "When I first I became general manager in 1979, aged 27, we had turnover of 12m Deutschmarks and debts of 7m.
"But we have always tried to deliver sporting success on the back of sound business practice. Now we generate turnover of €650m.
"There's turnover of €110m on shirts and fan merchandising alone. Compare that to 1979 when we only used to send out a few scarves, hats and postcards from our mailroom."