De Nicole, a 38-year-old escort claimed, "in the bed there was me, two girls from Rome and Berlusconi."
She also claimed that the prime minister gave them jewelery and many other gifts.
According the sources, Gianpaolo Tarantini, a businessman paid them to visit 73-year-old Berlusconi.
Meanwhile, Berlusconi maintained that he was unaware the women were paid.
De Nicolo told her interrogators about "the hours I slept alone and the hours when, instead, some hours, I was with other two girls."
However, this is not the first time that Italian PM comes under such scandal.
Another escort Patrizia D'Addario in 2009 released a tape in which Berlusconi told her to "touch herself" during sex.
D'Addario later published a book in which she praised Berlusconi for his sexual stamina and said he "deserved a place in the Guinness Book of Records."