Lille director general Frederic Paquet has issued a warning to Chelsea after reports they had announced their interest in Eden Hazard.
French sports paper L'Equipe put Hazard on its front page on Friday, claiming Chelsea had announced their interest in the winger and would be prepared to pay €25 million for him.
Chelsea are said to have contacted the player directly with a view to a move in the summer, while Hazard himself was said to have asked his agents to look at the proposal in more detail.
Paquet has been infuriated by the claims. "If Chelsea have contacted Eden, we are officially offended," he said in L'Equipe. "This is not the way things are done.
"It's been three years since Eden Hazard began attracting the interest of the top European clubs, but nobody is selling. We are currently holding discussions with Eden over how we can put together a long-term project with him, but maybe our message was not strong enough. We want to clarify it."
Hazard, 20, was twice voted best youngster in Ligue 1 and was in the team of the season for 2009-10. This season again he has been a significant factor for Lille, with his three goals and six assists helping the side to the top of the Ligue 1 table.
Arsenal's Arsene Wenger earlier this year voiced his admiration for the young winger, who at the time quoted Arsenal and Real Madrid as his dream destinations should he leave Lille.