The 20-year-old was targeted at Carrow Road during Liverpool’s 3-0 victory on the opening weekend of the English Premier League campaign as he made his Norwich City debut following a summer loan switch from Chelsea.
An offensive term was used during a rendition of ‘You’ll Never Walk Alone', the club’s anthem, which has been used before to direct a homophobic term at a Chelsea player.
The chanting was condemned by both Liverpool and Kop Outs, a LGBT+ fans group, on the day of the match and Kick It Out has followed suit.
They said in a statement: "We are disappointed that only two weeks into the English football season, we have already seen numerous incidents of discrimination at stadiums up and down the country.
"The use of the term 'rent boy' in chants by a portion of Liverpool fans at Carrow Road was unquestionably homophobic and has no place in our game. We have also had reports of incidents at other games and are awaiting further clarification.
"As always, we thank those who reported these incidents to us, and urge fans to do the same if they witness discrimination of any kind in football in the future. We will continue to liaise with all relevant clubs and the football authorities to identify and hold accountable those responsible."
The chanting was highlighted by Kops Out after the 3-0 win, secured through goals from Diego Jota, Roberto Firmino and Mohamed Salah.
They wrote on Twitter: “Great result today marred by homophobic chanting by some of our fans targeting Chelsea loanee Billy Gilmour. If you can't support without resorting to bigoted nonsense, you don't understand YNWA.”
This was quickly picked up on by the Anfield club, who tweeted their own disdain for the actions of some of the travelling supporters.
They said: “The chant is offensive and inappropriate - a message we have repeatedly communicated alongside Kop Outs. We urge supporters to remember the inclusive values of the club and to refrain from using it in the future.”
Though disappointed by the homophobic slur, Kops Out’ founder Paul Amann did praise the majority of Liverpool supporters for how they respond to both their and the club’s tweets.
He told Sky Sports: "You'll Never Walk Alone is an amazing anthem but to hear some of our own fans chanting in a way which leaves us feeling very alone is not on.
"The response to our tweet and the club's tweet has been absolutely enormous.
"It has been viewed over two million times and the vast majority of fans are supportive, they are engaging, they are realising, when they didn't, that actually that chant is quite homophobic.
"There are a few diehards, who quite frankly are somewhat in the stone ages on issues like this, but the vast majority are listening, and they are more than prepared to act as good allies in the future and to call it out and ask their fellow fans to tap them on the shoulder and say, 'don't chant that nonsense'."