The move comes as the octogenarian media mogul – who has been expelled from parliament after a tax fraud conviction – is trying to make a political comeback at the head of his centre-right Forza Italia party, which is polling around 12 percent.
Italian parties are jockeying for position ahead of the next general election, which will likely be in early 2018.
The prime minister’s office would not confirm or deny the report.
Three young women who participated in so-called “bunga bunga” sex parties at the former prime minister’s home and who subsequently testified against him in an earlier trial also filed as civil
plaintiffs, according to Italian news agency ANSA.
The trial opened on Wednesday, but other activity was adjourned to July 3.
Prosecutors suspect that Berlusconi paid nightclub dancer Karima El Mahroug – aka “Ruby Heart Stealer” – and other women who were summoned as defence witnesses more than €10-million (R146,97m) to make statements that helped the former premier avoid a conviction.
In the original case, focused on parties Berlusconi hosted in his villa outside Milan, the politician was accused of soliciting sex from El Mahroug when she was still underage and abusing his position as then prime minister to cover up the affair.
The affair became known as “bunga bunga” after the underground room where Berlusconi would entertain guests. In past trials, witnesses said the room hosted lap dance routines, sometimes by dancers wearing masks of famous people, such as former US president Barack Obama.
In 2015, he was acquitted of soliciting sex from a minor and abuse of power, after judges found insufficient proof that he knew El Mahroug was underage or that he pressured police to release her after she was held on suspicion of theft.
El Mahroug is herself on trial along with another 22 defendants for making false statements during proceedings against Berlusconi, which ended in 2015 with an acquittal for lack of evidence.
The other defendants include El Mahroug’s former lawyer Luca Giuliante, personal friends of Berlusconi such as Senator Mariarosaria Rossi and journalist Carlo Rossella, and several showgirls who were guests at his X-rated parties.