Anti-discrimination group Kick It Out have requested that Manchester United ask fans to stop singing a "racist" chant about new striker Romelu Lukaku.
Kick It Out say that the song's lyrics, which are about the size of the Belgium striker's penis, are "offensice and discriminatory".
"Racist stereotypes are never acceptable, irrespective of any intention to show support for a player," said Kick It Out.
Kick It Out said it was "aware of footage of alleged racist chanting by supporters of Manchester United that emerged on Wednesday 13 September", and the club have said that they will liaise with Kick It Out on matter.
United are also waiting to find out whether the chant is regarded as criminally racist, and therefore actionable.