Jose Mourinho believes that referees are being influenced by outside parties who are trying to convince the officials that Chelsea's players regularly dive.
The Portuguese coach's outburst came after referee Anthony Taylor booked Cesc Fabregas for simulation after the Spaniard was brought down by Matt Targett in the penalty area during yesterday's 1-1 draw with Southampton.
"There is a campaign against Chelsea," Mourinho said in a press conference. "I don't know why there is this campaign and I do not care.
"Everybody knows it was a penalty. The referee made a mistake, people make mistakes and he made a big mistake. He is a good referee and a good guy, he is young, he has years and years of football ahead of him but it is a big mistake."
Chelsea remain at the top of the Premier League table with a three-point lead over Manchester City.