Chelsea chairman Bruce Buck has written an open letter to fans condemning the actions of "a few mindless individuals" at some of their recent matches.
The club and the Metropolitan Police have opened investigations after alleged racist abuse was directed at Manchester City forward Raheem Sterling during the match at Stamford Bridge on December 8.
The Chelsea supporter accused has apologised for his behaviour, but denied he used racist language.
In his letter on the club's official website, Buck urged supporters to rally together to stamp out discrimination.
He said: "After recent events, I wanted to take this opportunity to reach out to our community and fans to condemn the actions of a few mindless individuals at some of our recent matches.
"These actions are unacceptable and unwelcome both in our club and in football.
"A deeply unpleasant but vocal minority which refuses to join us in the 21st century has shamed the great majority of our decent, well-behaved fans.
"We have been carrying out our own investigations into these events while cooperating fully with authorities.
"We have already suspended four individuals pending investigations and will continue to take the strongest possible action against anybody found to have been using discriminatory words or gestures. But we must all come together to stamp out these ugly scenes.
The 700-word letter outlined Chelsea's inclusion and diversity work, including the Say No to Anti-Semitism campaign launched in January and the joint campaign, launched in 2010 in collaboration with anti-discrimination group Kick It Out to "try and rid the game of the Y-word".
Buck, who has been chairman throughout the 15-year ownership of Russian billionaire Roman Abramovich, added: "The message from Mr Abramovich, our directors, our coaches, our players and our hundreds of staff is simple - this is a club open to everybody.
"We are committed and determined to be a force for good and not a symbol of society's wider problems.
"Clearly, there remains a way to go on this journey, but we will not rest until we have eliminated all forms of discrimination from our club.
"If you do not share these values, this is not the club for you. We are determined to win this battle, but we need the backing and action of those who share the principles of this great club."