Prosecutors also want to search several Milan apartments owned by Berlusconi where they believe he allowed the prostitutes to live. The investigation involves both prostitution and abuse of power.
Berlusconi, a billionaire media tycoon, is no stranger to scandal or court cases. But he no longer enjoys the same political support he once did, and last week a law shielding him from three unrelated trials was significantly watered down by Italy's constitutional court.
Milan prosecutors allege that Berlusconi had sex with "a number of prostitutes," according to the document.
Friends of the premier who are also targeted in the probe "identified, selected and accompanied a relevant number of young women, who prostituted themselves with Silvio Berlusconi in his residence and were paid money by him," even as the funds were distributed by intermediaries, Milan prosecutor Edmondo Bruti Liberti said, according to Bloomberg Businessweek.
But the key information in the document concerns Karima El Mahroug, now 18, a nightclub dancer better known as "Ruby." She told officials that she received about $9,300 after attending a party at Berlusconi's opulent villa outside Milan. Prosecutors allege that she was at Berlusconi's home more than once between February and May 2010 and that he paid to sleep with her. She was 17 at the time.
Prostitution is not illegal in Italy, but exploiting or aiding prostitution with someone under age 18 is an offense.
El Mahroug said last year she did not have sex with Berlusconi. But her description of the Milan sex parties as "bunga bunga" became a buzzword among global media last fall.
Berlusconi is also suspected of pressuring police into freeing Mahroug from custody when she was arrested on suspicion of theft, The Guardian reported.
Berlusconi denied all charges on Italian television Sunday night. His attorneys called the accusations "absurd and groundless." Berlusconi said he has never paid for sex and has been in a stable relationship since splitting up with his wife, Veronica Lario, who filed for divorce in 2009.
Lario said at the time she could no longer tolerate life with a man she said was "frequenting minors."
"It's absurd to even think that I would pay to have sex with a woman. It's something that has never happened even once in my life. I would consider it degrading," Berlusconi said, according to The Associated Press.
Berlusconi no longer can count on a secure parliamentary majority since a split last year with former ally Gianfranco Fini.
Named in the prosecutors' document was Nicole Minetti, a Lombardy regional official who was formerly Berlusconi's dental hygienist, Reuters reported. Minetti is accused of recruiting "a significant number of young women, who prostituted themselves with Silvio Berlusconi."
Minetti, who is also under investigation, denies the accusations.