Karima El Mahroug, the 18-year-old Moroccan dancer also known as "Ruby the Heartstealer," alleged that Berlusconi stepped in when she was arrested in an unrelated incident because he feared she would tell about his "bunga bunga" sex parties, The Daily Telegraph reported.
"Everyone was naked at the bunga bunga parties and when I was in the police station Silvio was scared," she allegedly told investigators.
Berlusconi allegedly paid El Mahroug for sex when she was 17. She said she met Berlusconi at a private party at his Villa San Marino mansion on Valentine's Day 2010.
She alleged that after dinner, Berlusconi, 74, invited her to join him and about 30 women in an underground "bunga bunga" room.
Berlusconi goes on trial on April 6 on charges he abused his office and for allegedly paying El Mahroug for sex.
Berlusconi has denied the allegations.