West Ham fans have been accused of homophobic chanting directed at Chelsea supporters during Saturday's game.
The Chelsea Supporters Trust said the chants of "Chelsea rent boys" were "continuous", while West Ham have said it does not condone the slurs which were heard at the Premier League game.
Following West Ham's 1-0 win at Stamford Bridge, Pride of Irons, West Ham's LGBT fan group, tweeted: "Having spoken to Chelsea Pride to get the details of yesterday's homophobic chanting, we understand that West Ham fans were chanting 'Chelsea Rent Boys'."
It said football equality campaign group Kick It Out has deemed the chants to be homophobic.
Pride of Irons added: "When you use homophobic chants you aren't abusing most Chelsea fans who will be straight, but all gay fans whether they support Chelsea or West Ham.
"We're better than that and can come up with much smarter chants that don't abuse our own fans.
"We shouldn't be the club appearing in the news for homophobia, there are other clubs who have ingrained problems. Let's not join their ranks.
"Be better. Be West Ham. Support the whole West Ham Family, no matter race, gender, sexuality or anything else."
Chelsea's official historian Rick Glanville said he reported the chanting to police after the game.
The Chelsea Supporters Trust said it noted "with dismay the continuous homophobic chanting" by West Ham fans, and said while it appeared no action was taken during the game, it wants Chelsea and West Ham to investigate.
Chelsea's LGBT fan group said it was "disgusted".
West Ham condemned the behaviour, with a spokesman saying: "West Ham United in no way condones any behaviour that falls short of the highest standards which the club sets when it comes to equality.
"At London Stadium against Arsenal on Monday night we will be celebrating and demonstrating the great work the club does to create a welcoming and inclusive environment for ALL supporters, including our LGBT+ fanbase, as part of our ongoing and unwavering support for the Rainbow Laces campaign."
A Chelsea spokesman told Sky Sports News: "Just as we criticise our supporters when they have been guilty of discriminatory behaviour, we expect other clubs to stand up, speak out and do the same."
In April, Liverpool warned its fans about homophobic chanting directed at Chelsea supporters.
Nottingham Forest fans were investigated in January after using the "Chelsea rent boys" chant during a game.
Also in January, a Chelsea fan was fined £965 and banned from attending football matches for three years for chanting homophobic slurs during a Brighton game last December.