Perez was on the receiving end of a five-second penalty for hitting McLaren's Lando Norris when he tried to overtake the Briton.
The Red Bull driver argued Norris was to blame as he felt he was ahead, while Norris said he was actually making room to let Perez pass on purpose, although the Mexican crashed into him anyway.
At the time, Perez vehemently disagreed with the penalty, which demoted him from second to fourth at the finish.
After crossing the finish line he further lashed out at the stewards on the team radio, saying: "The stewards are a joke, man. I cannot believe it. They have been very bad this year, but this is a joke. That was really a joke."
The stewards summoned Perez for his comments and, after receiving an apology, they settled on giving him a formal warning.
In their verdict, the stewards said they have no issue with public criticism, but thought Perez crossed the line of "personal insults", which is in breach of Article 12.2.1 k) of the International Sporting Code.
Source: Autosport