The Chelsea chairman, Bruce Buck, has attacked a minority element of the club's support for anti-semitic abuse of the new manager, Avram Grant.
The Israeli's appointment after Jose Mourinho's departure from Stamford Bridge has provoked strong feeling but Buck said some of the comment which the club had received crossed the boundaries of acceptability.
"We welcome all constructive points of view," Buck wrote in Saturday's match programme for the visit of Fulham. "But there have been a few which could be viewed as racist and anti-semitic and that must stop immediately. This is one thing we will not tolerate whether in written correspondence, on the chat pages, on posters or banners or through singing and chanting. And it unfairly smears the reputation of the vast majority of Chelsea fans who rightly do not want to be associated with such activity."