Dr Helmut Marko says Red Bull is not joining those who are pointing fingers of suspicion at Ferrari.
For the first time in the 'power unit' era, Ferrari is now clearly ahead of Mercedes with its Formula 1 engine.
It is believed the Italian team has devised a clever but controversial system to get more electrical power than expected out of its hybrid elements.
Mercedes is sceptical.
"I'm not saying that it's true, but if someone was prepared to risk their reputation, then there is very little possibility of policing this.
It's a highly complex technology. So with all the scepticism and paranoia that exists in F1, we have to trust the integrity of people and organisations, and we do that," he told Auto Bild.
Eyebrows raised at Mercedes
"We trust the FIA and we trust our competitors, because that is the only way we can compete on a Sunday," said boss Toto Wolff.
But Red Bull's Marko raises his eyebrows not at Ferrari, but at the suspicions being cast on the Italian team by Mercedes.
"Mercedes had the best engine for four years, but now Ferrari does. They should accept that and not wash their dirty clothes. At Red Bull, we do not participate in these rumours. We know what Sebastian (Vettel) can do, including in engine development.
He has made sure that Ferrari overtook Mercedes. Now Mercedes always needs luck to win. If everything goes normally, Ferrari is ahead," Marko added.