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 Louis, 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 willing 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."
Louis told the Sun the allegations were "wholly false and without foundation" and said he was confident he would be "fully exonerated".
The Irish 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.