Lukas Podolski is expected to be fined by Cologne after claims he made in the German media.
The 26-year-old recently told Bild am Sonntag that the club have not lived up to promises that they would build a side around him.
"These statements are an affront against the club," club executive Claus Horstmann told Express. "The time and content of these statements comes as a total surprise to me.
"If you are asking for patience and silence and then step up to commit such an interview, I am unaware of the self-conception that must be behind that.
"I do not know what the idea is behind this. All I am to say is that this is a true breach of contractual agreement, once again. We are to sanction this."
Podolski has been linked with a move to Premier League side Arsenal.