McLaren boss Zak Brown has branded Red Bull, Aston Martin, and Williams as cheats in a letter to the FIA, Formula 1, and six fellow teams.

Brown’s assessment comes off the back of the Certificate of Compliance process relating to last year’s Financial Regulations.

Released last week, it was revealed six of the 10 current F1 teams were in full compliance with the regulations, while three were not.

Two of those, namely Aston Martin and Williams, were procedural breaches while Red Bull was found to have made a ‘minor’ overspend.

The precise figure of that overspending, and its nature, are yet to be confirmed; however, sources have suggested to Speedcafe.com that the figure is in the region of $1.5 million.

It’s thought that relates to a high-value staff member, though not Adrian Newey as some have claimed, and the perks offered to members of staff that were not accounted for in their salary packaging.

The overspend is not believed to have related to any performance-related aspects of the team’s operation, with the FIA’s interpretation of the costs different to those of Red Bull, which had them excluded from the cost cap.

It was during the audit process which began following teams’ submissions in March that the issue was highlighted, with rivals breaking ranks in Singapore to expose it to the media.

McLaren was not among those publicly throwing mud at the time and has instead raised its issues behind closed doors – only for Brown’s missive to now find its way into the public domain.

“As the investigation demonstrated, of the ten teams reviewed, seven were found in total compliance with the Cost Cap rules,” Brown wrote in the letter, addressed primarily to FIA President Mohammed Ben Sulayem, dated October 12.

“One team was guilty of a minor overspend breach plus a procedural breach, and two further teams also in procedural breach.

“The overspend breach, and possibly the procedural breaches, constitute cheating by offering a significant advantage across technical, sporting, and financial regulations.

“The FIA has run an extremely thorough, collaborative, and open process, we have even been given a 1-year dress rehearsal with ample opportunity to seek any clarification if details were unclear. So, there is no reason for any team to now say they are surprised.

“The bottom line is any team who has overspent has gained an unfair advantage both in the current and following-year’s car development.”

Financial Regulations were first introduced to Formula 1 last season, with this their first real test.

As a result, the sport is in uncharted territory. The FIA’s response is therefore critical; a soft penalty will undermine the ruleset and jeopardise Formula 1 at a very fundamental level.

That is why Brown joined his fellow team bosses and has called for harsh penalties to be applied.

“We don’t feel a financial penalty alone would be a suitable penalty for a overspend breach or a serious procedural breach, there clearly needs to be a sporting penalty in these instances, as determined by the FIA,” Brown’s letter stated.

“We suggest that the overspend should be penalised by way of a reduction to the team’s cost cap in the year following the ruling and the penalty should be equal to the overspend plus a further fine i.e. an overspend of $2M in 2021, which is identified in 2022, would result in a $4M deduction in 2023 ($2M to offset the overspend plus $2M fine).

“For context $2M is 25 – 50% upgrade to annual car development budget and hence would have a significant positive and long lasting benefit.

“In addition, we believe there should be minor overspend sporting penalties of a 20% reduction in CFD and wind tunnel time.

“These should be enforced in the following year, to mitigate against the unfair advantage the team has and will continue to benefit from.

“To avoid teams accumulating and benefitting from the multiplier effect of several minor overspend breaches, we suggest that a second minor overspend breach automatically moves the team to a major breach.

“Finally, given the financials involved, a 5% threshold for a minor overspend breach seem far too large of a variance, we suggest a lower threshold 2.5% is more appropriate.”

Should Brown’s suggested penalty be adopted, it would almost certainly put Red Bull in breach again this year as, with four races to go, there is little opportunity to reduce its spending.

The knock-on being that it would take a further hit next season – a point that is unlikely to have escaped Brown.

CLICK HERE to read the letter in full