Saint-Etienne has filed a legal complaint after several Lyon players joined their fans in singing offensive chants about the French club as they celebrated winning the French Cup.
Saint-Etienne said Tuesday that it had filed the complaint with the prosecutor's office, which will decide whether to pursue the case.
Lyon ended its four-year wait for a trophy by beating semiprofessional side Quevilly 1-0 on Saturday.
The next day, Lyon's players paraded the trophy in the city center and several players - including club captain Cris, Maxime Gonalons, Alexandre Lacazette and Jimmy Briand - joined the fans in singing insulting songs about Saint-Etienne.
''It is unacceptable that Lyon players sing an offensive song together on a hotel balcony in Lyon during a ceremony,'' Saint-Etienne said in a statement. ''In light of these vile insults, which are criminally reprehensible, the club has decided to file a complaint.''
Matches between the local rivals are often heated and have led to clashes between fans in previous years.
''In the sporting context known to everyone, no verbal violence from the part of players or directors can be tolerated,'' Saint-Etienne said.
Veteran goalkeeper Jeremie Janot, who has played for Saint-Etienne since 1996, said the behavior of Lyon's players was irresponsible.
''If, by misfortune, there are incidents and injuries at the next derby then they will be largely responsible,'' he said on Twitter. ''They have stirred up hatred.''
The French league's ethics committee also said it will investigate.
Last season, Marseille left back Taye Taiwo was fined and suspended for one game for joining along with fans in singing a homophobic song about bitter rival Paris Saint-Germain after his team had beaten Montpellier 1-0 to win the League Cup.
