West Ham's owners have issued a warning ahead of Monday night's visit of Tottenham that they have a zero-tolerance approach to any racist behaviour by supporters.
The Football Association is investigating allegations of anti-Semitic abuse at the previous encounter between the two sides at White Hart Lane earlier this season. And in a message to fans, the Hammers' co-owners David Gold and David Sullivan have warned the club will not tolerate any incidences of racism at Upton Park.
Gold and Sullivan said in a statement: "There are occasions when individuals still act in an inappropriate way and we have a simple zero-tolerance policy when those isolated incidents do occur at matches at the Boleyn Ground."
The statement continued: "Working with the Metropolitan Police, we will pursue the harshest sanctions against any individual who goes against what we stand for as a club, and in the rare case that you do see or hear anything you think is unacceptable, there are a number of ways you can report the matter.
"The club is extremely proud of its work in supporting programmes that promote tolerance and inclusion, and you will have seen more evidence of that this week as we push the message of the Football v Homophobia campaign.
"West Ham United were one of the first professional football clubs to lend its support to this important movement, and our work there sits alongside our support of Kick it Out, Holocaust Memorial Day, Black History Month, Inter-Faith Week and many other key initiatives."
After the match on November 25, the FA launched an investigation into reports of the abuse, while West Ham banned one of two fans cautioned by police.
A section of Hammers fans had appeared to mock both the gassing of Jews in the Holocaust and the knife attack on a Spurs fan before Tottenham's game in Rome last week.
West Ham's Israeli international Yossi Benayoun also spoke of his disappointment and embarrassment at hearing anti-Semitic abuse by some of the club's fans towards Tottenham's supporters.
There were also reportedly chants about Adolf Hitler during the match, which Spurs won 3-1. The chants were also reported to the police by the Society of Black Lawyers.