McLaren CEO Zak Brown has written to FIA president Mohammed Ben Sulayem urging him to tighten up Formula 1’s rules to "eliminate" alliances between teams.

The subject of collaboration between teams has become a hot topic again in F1 with Mercedes interested in taking a financial stake in the Alpine squad.

While Brown’s criticisms of the situation are not aimed directly at Mercedes, he has made clear that his stance against closer ties between squads counts for all parties.

Speaking at the McLaren factory recently, Brown said: "It applies to anybody and everybody. So A/B teams, co-ownership, regardless of who it is, I frown upon it.

"I don't think it's healthy for the sport. But it's not personal or towards any one team or individual."

Now Brown has made his stance more formal in writing a lengthy letter to Ben Sulayem asking him to take action to protect the integrity of F1.

In the six-page letter, a copy of which has been seen by The Race, Brown argues that the financial health of F1 now means that single entities owning multiple squads is not necessary and is unfair on independents.

The letter makes no direct reference to Mercedes and Alpine, and is instead focused entirely on the concept of team partnerships.

"There is a real concern that the sport risks taking a step backwards in terms of integrity and fairness, at a time when the regulatory framework has been designed – with significant collective effort – to move in the opposite direction," wrote Brown.

He cited several examples of circumstances where he believes sporting integrity has been damaged by teams working in alliance – such as Daniel Ricciardo taking the fastest lap for Racing Bulls at the 2024 Singapore Grand Prix to deny McLaren a point there when its driver Lando Norris was fighting Red Bull’s Max Verstappen for the title, and Racing Bulls’ Liam Lawson being asked to move aside for Verstappen in the recent Miami GP.

There are also arguments put forward that shared resources, including windtunnels and software, can provide benefits if used across teams that are not available to those working alone.

Furthermore, he questions why McLaren had to wait nine months, and pay compensation for Rob Marshall to move from Red Bull in 2024, while Laurent Mekies was able to switch being team boss from Racing Bulls to Red Bull in a matter of days.

He also says that Andrea Landi’s move from Racing Bulls to Red Bull that will take place on July 1, having been announced on April 17, "reinforces" perception that internal firewalls are not operating in a way that would be accepted between "genuinely independent competitors."

Brown argued that it was a matter of "fairness" that teams had no formal ties.

He wrote: "We need to eliminate any further alliances, whether through ownership, strategic participation or any other equivalent form of control or influence, and we need to work together quickly to start the process of unwinding those already established to ensure that the future integrity of the sport is not compromised."

Brown said in the letter that he would welcome the opportunity to discuss the matter with Ben Sulayem and that McLaren will start working on recommendations for how governance can address issues through changes in the regulations.

The letter finished: "I think the work that the FIA and Liberty have done to create 11 healthy teams, in a cost-controlled environment, has created the most competitive era of Formula 1 ever.

"We believe that, by addressing this remaining structural issue, Formula 1 will be set on an even stronger course, will continue to thrive and be the best the sport has ever been, we just need to make sure we bring total parity and integrity to the sport in every aspect. I am confident we can achieve that together."

Ben Sulayem has already been aware of the concerns expressed by Brown about co-operation between teams. Speaking to media at the Miami Grand Prix he made clear that it was a matter he was looking into.

"I do believe that owning two [teams] is not the right way – this is my personal point of view – but we are looking into that because it’s a complicated area," he was quoted as saying by Reuters.

"We put our people to see, is it possible? Is it allowed? Is it the right thing? There is something called a sporting side. If we lose the sporting spirit, I believe that there will not be any more support [from F1 fans]. So to me, I’m not with it 100%."