Louis Walsh has "vigorously denied" allegations that he indecently assaulted a 24-year-old man.
According to The Sun newspaper, police are investigating claims against the X Factor judge over the alleged incident in a nightclub at a hotel in Dublin.
A spokeswoman for Walsh, 58, said he would "willingly co-operate" with any investigation, but stressed he had not been contacted by police about the claims.
The spokeswoman said: "He vigorously denies all of the allegations. If contacted by the police he will willingly co-operate with any investigation. Louis categorically denies any wrongdoing and will fight to clear his name."
She added: "The fact of the matter is the police have made no contact with Louis whatsoever."
The newspaper quoted a police source as saying: "An investigation is ongoing."
Walsh told The Sun the allegations were "wholly false and without foundation" and said he was confident he would be "fully exonerated".
The star became a household name in 2004 when he became a judge on the X Factor, and is the only remaining member of the original panel.
He has managed a number of groups and performers, including boybands Boyzone and Westlife.
A spokesman from An Garda Siochana said it does not comment on named individuals or individual investigations.