"I say it very clearly: there is no team play at this level in Formula 1," Berger said to Kolner Express.
"I don't know if he fooled Vettel, but it's been clear for a long time that Leclerc has an absolute killer instinct. Vettel can never rely on him. Good faith has little place in top-level sport."
"It's quite simple," Berger said. "If you lose your instincts, then you no longer have the claim to become world champion. Then you have to get them back again."
Many believe that Leclerc's political power could be part of why he wasn't penalized at the Italian Grand Prix. His manager is Nicolas Todt - the son of FIA president Jean Todt.
"I don't think that matters," Berger said. "If Vettel spins or Leclerc does not stick to the agreement on slipstreaming, neither the FIA president or a manager can take care of that."
Vettel will need to go back to his old self if he is to get the better of the aggressive style of his teammate.