The chant was seemingly directed at Everton manager Frank Lampard during the second half of the match at Old Trafford, and referred to his long association with Chelsea where he was both a player and manager.
A statement from the governing body said: “We strongly condemn the use of the term ‘rent boy’ and we are determined to drive it out of our game.
“We continue to work closely with the Crown Prosecution Service, as well as the UK Football Policing Unit, in relation to the use of this term.
“Part of our work in this area has been to provide the relevant authorities with impact statements from LGBTQ+ supporters, detailing how chants of this nature affects their experience and feeling of inclusion at football matches, so that a clearer stance and understanding on the chant can be established.
“We stand firmly against all forms of discrimination and we are striving to ensure our game is a safe environment for all, which truly embraces diversity and challenges hateful conduct both on and off the pitch.”
A statement from United said: “Homophobia, like all forms of discrimination, has no place in football. Manchester United is proud of our diverse fan base and the work we have done to reduce instances like we sadly heard today.
“We will continue to campaign for inclusivity and to tackle discriminatory abuse whether inside stadiums or online. This includes working with fan groups to educate fans on the offence which discriminatory language causes.”
Rainbow Devils, United’s LGBTQ+ supporters’ group, called on the club to identify those responsible for the chants and to take action.
“We strongly condemn the taunting of Frank Lampard with the illegal and homophobic chant from a section of our fans and call for the club to take action,” the group said in a tweet.
“We call on Manchester United to do everything in their power to identify the culprits and deal with them in the strongest possible manner.”