Silvio Berlusconi resigned as prime minister in November 2011, ending a scandal-plagued era Italian history [Reuters]

The trial of Silvio Berlusconi, the former Italian prime minister, for having sex with an underage prostitute has opened amid lurid disclosures about the hard-partying lifestyle of the ex-head of state.

Model Imane Fadil said on Monday the first time she went to a party she was given $2,600 in cash by Berlusconi, who told her: "Don't be offended."

That night she said she saw two young women in costumes with "black tunics, white veils and crosses" stripping in front of the then prime minister.

One of the two was Nicole Minetti, now a regional councillor for Berlusconi's People of Freedom party in Milan, Moroccan-born Fadil said.

She claimed Minetti and the other woman stayed the night at the villa near Milan and said women who remained got more money to have sex with Berlusconi.

Berlusconi is charged with having sex with an underage prostitute, Moroccan Karima El-Mahroug, and then allegedly abusing his powers by getting police to release her when she was arrested for theft to hide his crime.

He was not in court on Monday but is due to testify later in the trial.

Judicial impasse

El-Mahroug, a dancer who was 17 when she allegedly had sex with the prime minister, is better known by her stage name of "Ruby the Heart Stealer".

Berlusconi rejects all charges and El-Mahroug denies having sex with him.

The billionaire tycoon was ousted from power in November 2011 following a parliamentary revolt against his increasingly scandal-tainted rule and a wave of panic on the financial markets that pushed Italy to the brink of default.

He is a defendant in two other trials, for tax fraud and for violating official secrets. An Italian court this year threw out separate bribery charges against him under the statute of limitations following a five-year trial.

Despite his being convicted several times of corruption and false accounting in the past, all cases against Berlusconi have either been overturned or expired after years of moving laboriously through Italy's justice system.