Chelsea chairman Bruce Buck has hit back at fans who sent racist messages to the club after their appointment of Israeli coach Avram Grant.
The Premier League club hired Grant as Jose Mourinho's replacement two weeks ago and Buck revealed there has been an element of racism and anti-Semitism to some Blues fans' protests at the decision.
The comments will be particularly upsetting for Grant as the 52-year-old's Polish father Meir is a Holocaust survivor.
Buck wants the abuse to stop immediately.
"We welcome all constructive points of view," he said. "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.
"It unfairly smears the reputation of the vast majority of the Chelsea fans who rightly do not want to be associated with such activity."