has Italian Prime Minister Silvio Berlusconi laughed off an enquiry into his bawdy sex life and relationship with an underage girl as magistrates struggled to get permission to search his offices for evidence against him.

Milan's prosecutors hit a hitch today in their endeavour to prove Berlusconi hooked up with prostitutes he kept in rent-free luxury apartments, when a parliamentary committee stalled over authorising the search warrant.

Allegations that the prime minister hand-picked prostitutes for wild parties and paid to have sex with the underage girl, known as Ruby, left Italy reeling this week and sparked fierce criticism from the Church and opposition parties.

News of the investigation came just the day after a court ruling partially stripped the prime minister of political immunity.

While having sex with prostitutes is not a crime in Italy, having sex with a minor has been punishable with a prison sentence since Berlusconi's right-wing government voted in a law against it in 2006.

"A significant number of young girls prostituted themselves with Silvio Berlusconi in his residences in exchange for sums of money," prosecutors said in a document asking the Chamber of Deputies for permission to raid various premises linked to Berlusconi.

In wire taps of conversations between Ruby and friends, the Moroccan, whose real name is Karima El Mahroug, said she had asked Berlusconi for five million euros compensation for having sullied her name.

Berlusconi on Tuesday evening dismissed the allegations as a "media construction" and said he had no intention of resigning. "Are you mad?" he retorted when questioned by journalists. "I'm having fun!"

The prosecutors hope to search the offices of Berlusconi's trusted sidekick Giuseppe Spinelli, who manages the prime minister's Fininvest holdings and is suspected of unwittingly handling money for Berlusconi's prostitutes.

Spinelli's offices are considered part of Berlusconi's domain.

But on Wednesday Italy's parliamentary committee speaker, a member of Berlusconi's centre-right party, postponed the decision by at least a week, claiming to need more time to read the prosecution's 389-page document.

Milan's magistrates, lead by fearful mafia-hunter Ilda Boccassini -- nicknamed Ilda the Red by Italian media thanks to her flame-coloured hair -- may be running out of time to find the evidence they insist is there.

Berlusconi has said he is convinced parliament will move to take the case from Milan's prosecutor's office and hand it over to the minister's court, where it will most likely be dropped.

Prosecutors have demanded Berlusconi submit to interrogation this month, but the prime minister has dismissed the idea. "My lawyers said that as the Milan tribunal is not qualified (to judge this case) it's not logical for me to go."

The Church described allegations that Berlusconi paid for sex with a minor as "harmful and shocking," with the Influential Roman Catholic daily Avvenire on Tuesday calling for Berlusconi to clean up his act.

As the Italian media worked themselves into a frenzy over the scandal and experts warned the country's image would be damaged abroad, President Giorgio Napolitano called on Milan's prosecutor to speed up the enquiry.

The leader of the opposition Democratic Party (PD), Pier Luigi Bersani, called on Berlusconi to resign and submit himself to the inquiry.

Media magnate Berlusconi, a notorious womaniser, has previously admitted he is "no saint" but claimed he never paid for sex, insisting that he has been in a stable relationship since splitting up with his wife Veronica Lario in 2009.

Both he and Ruby, a disco dancer who is now 18, have denied having had sexual relations.

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