Aaliyah Reed, who was 17 years old at the time of the alleged incident, claimed that Boateng, 24, asked for her phone number and took her Snapchat details in July 2018.
Reed, now 18, said she made a formal complaint to Greater Manchester Police at the time.
“He came over to me and said, ‘Come with me and I’ll show you around Manchester. I’ll show you a good time,’” she told The Sun.
“He asked for my number. I said my phone was broken, the SIM card wasn’t working, so he asked for my Snapchat.
“I gave him it and he got back in the car and left.”
Greater Manchester Police told The Sun: “Allegations were made regarding an officer in 2018 and 2019 which are currently under investigation by the Professional Standards Branch.
“It is inappropriate to comment further whilst the investigation is ongoing.”
Standard Online has contacted representatives for Love Island and Greater Manchester Police for further comment.
Speaking ahead of his entrance to the villa, Boateng confirmed that he resigned from the police in order to take part in Love Island.
He said that he has a “good relationship” with chief constable Ian Hopkins and claimed that the force has “left the door open for me to come back if I do want to come back.”