McLaren Chief Executive Officer Zak Brown (L) and Red Bull Racing's British team principal Christian Horner (R) address the media in Austin on Saturday

Austin (AFP) - Red Bull boss Christian Horner on Saturday hit out at McLaren counterpart Zak Brown for making “shocking” accusations of cheating over breaches of Formula One’s cost cap regulations.

Speaking at a press conference ahead of Sunday’s United States Grand Prix, Horner slammed Brown over a letter the McLaren chief wrote to the International Motoring Federation (FIA) in relation to Red Bull’s cost cap breach.

The FIA released a report two weeks ago in which Red Bull was declared as having broken the newly-established spending limit of $145 million in the 2021 season.

Brown’s letter to the FIA and F1 chiefs said any breach of the financial regulations “constitutes cheating.”

That drew a fiery response from Horner during Saturday’s press conference where he sat alongside Brown, insisting that Red Bull “absolutely and categorically” had not benefited from the rules breach.

Asked for his views on Brown’s letter, Horner replied: “It’s tremendously disappointing 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, without any knowledge of the details, can be making those kind of accusations.”

Horner said Red Bull had been “on trial” because of accusations made in the wake of the Singapore Grand Prix earlier this month, with the team subjected to “the rhetoric of cheats”.

“We’re getting kids of employees bullied in playgrounds. That is not right,” Horner said. “Because of fictitious allegations from other teams.

“You cannot go around just making that kind of allegation without any fact or substance.

“We absolutely are appalled at the behaviour of some of our competitors.”

Brown meanwhile insisted he had been intending to make a “general response” to the cost cap controversy.

“My letter set out I think that, if a team spends more than the cap, they are going to get an advantage and the cap is a rule – no different to the technical rules in the sport,” Brown said.

“We are not taking a view whether they did or didn’t…It didn’t mention any teams. It was a general response, now that we are into the cost cap era, if someone breaches that, here’s what we think some of the ramifications are.”

Red Bull are currently negotiating with the FIA to find agreement on what they can accept as a breach and a suitable level of punishment, which could be a fine or a points penalty.

“We had zero benefit from a development perspective or an operational perspective either for 2021 or for 2022… Our submission was significantly below the cap,” Horner said.