McLaren CEO Zak Brown has raised concerns about the relationship between Red Bull and its junior team, AlphaTauri, as "something that needs to be addressed in the future".
Red Bull has owned two F1 teams since the mid-2000s -- it bought the Jaguar team for the 2005 season, before purchasing Italian-based Minardi the following year and naming it Toro Rosso.
Toro Rosso was renamed AlphaTauri, after Red Bull's fashion brand, in 2021, but still operates out of the same HQ in Faenza, Italy.
The world champions recorded the most dominant F1 season in history this year and by early July had stopped working on the dominant RB19 and started on its successor.
AlphaTauri, by comparison, upgraded its car until the last race of the year.
Brown, who's McLaren team emerged as Red Bull's closest competitor in the second half of the season, wants the partnership between the two teams to be looked at.
In an interview with Autosport, Brown said: "The million-dollar question that none of us know is how early did they [Red Bull] turn off this year's car?
"We know we've outperformed the others in the development race, and we know we've closed the gap to Red Bull but what none of us know is: did Red Bull stop, and we just caught up, or were they still developing?
"Also, we have some big concerns over the alliance between AlphaTauri and Red Bull. I think that is something that needs to be addressed in the future.
"So, I still think the sport has a way to go to make sure that everyone is truly independent."
What the Red Bull-AlphaTauri partnership will look like going forward has been a major talking point since the death of Red Bull founder Dietrich Mateschitz in October 2022.
Mateschitz's son, Mark, who owns 49 percent of the company, resisted pressure internally to sell AlphaTauri, saying his father's ambition had always been to have two teams on the grid.
Red Bull spent much of the year in talks with various companies, which ESPN understands included JP Morgan and Hugo Boss, about a naming partnership, but so far a deal has failed to materialise.
AlphaTauri will race with Daniel Ricciardo and Yuki Tsunoda in 2024.