Italy's Prime Minister Silvio Berlusconi has succeeded in blocking publication of photos of his New Year's Eve party after reports said guests included a teenage girl whose relationship with him has caused a scandal.

Judicial sources said the 72-year-old Berlusconi, who denies having an affair with 18-year-old Noemi Letizia, said publication of the images taken by a photojournalist without his permission would have violated his right to privacy.

A prosecutor in Rome granted the injunction and ordered the seizure of hundreds of photos taken by Antonello Zappadu using a powerful lens from outside Berlusconi's villa on the Mediterranean island of Sardinia.

Newspapers have reported that dozens of young women attended the party thrown by the media billionaire-turned-politician, receiving thousands of euros in expenses.

Berlusconi's personal life has under scrutiny since he was photographed attending Letizia's 18th birthday party in Naples last month, where he gave her an expensive necklace. He says he has known the family for years. His wife Veronica Lario demanded a divorce because of his womanising, accusing him of "frequenting minors" and saying he was "not well".

Berlusconi on Thursday denied any improper relationship and said he would resign if caught lying about it.

The case has rattled Berlusconi's conservative Roman Catholic support base before European elections in early June. Church figures have criticised him for setting a bad example to young people with his behaviour.

The age of consent for sex in Italy is 16 but people under 18 are considered minors.

The case has become so politically explosive that Berlusconi has promised to clear his name with a formal address to parliament but has not yet set a date.