Juventus chairman Andrea Agnelli has led proposals to revamp the competition, with the intention of including more matches and introducing some form of promotion and relegation in 2024.
Initial plans have been put forward by the European Club Association (ECA), of which Rummenigge was chairman from 2008 until 2017.
"Why do we have to change anything?” Rummenigge asked Bild.
"I'm also not a big fan of the idea to expand the group stage. At the end of the current model with the groups of four, we often end up with so-called ‘dead games’, where everything is already decided.
"Everyone is always running after the money. But where is this money going?
“It isn’t like our profits exploded and our shareholders also shared in this success. The money is being spent on players’ wages and agents’ fees.
“Most importantly, the European Cup will not take place on the weekends. Because that would create too big a fight with the national leagues.”
Rummenigge, 63, won the European Cup twice as a player with Bayern in the 1970s and as a former chairman of the ECA, his opinion on the matter could carry some significant weight.
He is not the only high-profile opponent, with the Premier League already having issued a statement underlining their opposition to any reforms “that would alter the structures, calendar and competitiveness of the domestic game”.
Closer to home, Rummenigge also repeated his support for Bayern manager Niko Kovac, who had been linked with an early dismissal from the club.
Bayern started the season poorly and looked like surrendering their Bundesliga crown to Borussia Dortmund – but finished the campaign in style with a domestic double.
"I do not know any club that would have dismissed their coach after winning the double," said Rummenigge.
Rumours of his sacking had in part been due to Rummenigge’s lack of public backing for the coach during the season, but he claims he had Kovac’s best interests at heart.
"I did not want to hurt him. I just wanted to focus everyone on our common goal.
"Success is part of our club’s DNA. We have imposed this pressure on ourselves, and everyone must withstand that at Bayern. Niko knows that, he has already worked as a player here.”