Sex parties at Italian Prime Minister Silvio Berlusconi''s palatial villa followed a well scripted routine drawing in erotic dancers and underage prostitutes, the Italian Prosecution will claim on Wednesday.

First came dinner; a meal often composed of foods in the red, white and green of Italy''s tricolour flag.

Then followed what has become known as the "bunga bunga" session, "which took place in a disco-like room where the female participants engaged in dressing up, striptease and erotic dances, touching each other or touching and being touched in their intimate parts by Silvio Berlusconi."

Finally, at the end of the evening, 74-year-old Berlusconi would choose "one or more women with whom he spent the night in an intimate relationship," in exchange for money, expensive gifts or rent-free apartments.

The scandal has eaten away at the popularity of the media billionaire and cast a shadow on a political system dogged by corruption scandals throughout the post-war era. But he is in little danger of being forced from office before a verdict which may take years or may never come.

Prosecution documents list the names of 33 young women, mostly would-be starlets hoping to break into showbusiness on one of Berlusconi''s television channels, who prosecutors say were paid to have sex with him.

For Berlusconi, who will not be present when the trial opens, only one of them matters: She is Karima El Mahroug, a Moroccan nightclub dancer known by the stage name of Ruby "Rubacuori" ("Heartstealer"). She was 17 when, according to the prosecutors, she was paid to have sex with him. Paying for sex with a woman under 18 is a crime in Italy.

In a tearful interview on one of Berlusconi''s TV channels Ruby claimed that, after being sexually abused as a child, she "invented a parallel life". She said Berlusconi "never laid a finger on me", did not know she was a minor and only gave her 7,000 euros ($9,845) after a party because she had told him she was in trouble.

She also says she has only been to his villa three times, wants to put "all this mess" behind her and marry her boyfriend.

In leaked wiretaps of her telephone conversations, however, she told friends that Berlusconi had offered to "cover her in gold" to keep quiet, and that she had demanded 5 million euros. Mobile phone records place her at the Arcore villa 13 times between February and May 2010.

In the trial, Berlusconi is also accused of abuse of office, by intervening to have El Mahroug released from a Milan police station last May as a cover-up, after she was accused of stealing a 3,000-euro bracelet.

Even Berlusconi''s lawyers acknowledge that he personally phoned police officers and told them he believed El Mahroug to be the niece of former Egyptian president Hosni Mubarak, although they say he did not exert improper influence.

Berlusconi denies all charges. He says he likes women and is "no saint" but has never paid for sex. Parties at his villa in Arcore, a small town outside Milan, are normal, "convivial" dinners with lots of food, laughter and jokes.

The gifts and money he gave to some of the women, he says, were just his own, generous, way of helping people in need and well within his means as one of Italy''s richest men.

He accuses leftist magistrates of waging a political, moralistic campaign to oust him from power and has frequently decried the wiretaps used on the phones of his guests.