Tempers boiled over at a press conference as Christian Horner shared his disgust with fellow Formula 1 team principal Zak Brown over accusations made in a letter to the FIA.
The McLaren chief wrote to the sport's governing body demanding harsh penalties for any team which breaches cost cap rules, in the wake of the accusation that Red Bull did exactly that last season. That letter was leaked, and was a source of contention as the two team bosses met the media on Saturday.
Horner and Brown were seated next to one another at a press conference in Austin which promised to produce fireworks. And that is exactly what happened, as the Red Bull boss struggled to contain his anger after being asked for his reaction to the letter.
"Obviously Zak's letter, which wasn't copied to us – we've had sight of the letter – is tremendously disappointing," he told reporters. "For a fellow competitor to be accusing you of cheating, to accuse you of fraudulent activity is shocking.
"It's absolutely shocking that another competitor, without the facts and without any knowledge of the details, can be making that kind of accusation. We've been on trial because of public accusations since Singapore, the rhetoric of 'cheats', the rhetoric that we've had this enormous benefit, and numbers that have been put out in the media that are miles out of reality.
"The damage that does to the brand, our partners, our drivers, our workforce, in an age where mental health is prevalent – we're seeing significant issues within our workforce, including employees' kids being bullied in playgrounds – that is not right.
"Through fictitious allegations from other teams, you cannot go round making that kind of allegation without any fact or substance, so we are absolutely appalled at the behaviour of some of our competitors."
While Horner's emotions were plain to see, Brown maintained a straight face and chose not to give a confrontational response. The McLaren boss said: "My letter set out that I think if a team spends more than the cap, they're going to get an advantage. The cap is a rule, no different than the technical rules in the sport.
"We're not taking a view whether they did or didn't [overspend], my letter was 'if someone has, then here are the things we think should be addressed', no different than if ride height is incorrect, or a flexi wing, whatever. I didn't mention any teams, it was a general response that now we are in the cost cap era, if someone breaches that here is what we think some of the ramifications are.
"I have no idea what the number is, I know none of the detail. But if we had more money to spend then that would put us in a better light and performance, more people, more upgrades, whatever the case may be. We feel the performance benefit, if someone has spend more than the allocated cost cap, it is up to the FIA to determine whether they have or haven't."
