His lawyer, meanwhile, moved to sue Spanish newspaper El Pais for having published photographs of topless women and a naked man lounging at the premier's Sardinian home. Last week, Italian prosecutors seized the pictures and placed the photographer under investigation for alleged violation of privacy.
The photos came to light amid a scandal involving Berlusconi and Naples model Noemi Letizia, whose 18th birthday party the premier attended several weeks ago. Berlusconi's wife cited the premier's attendance at the party in announcing she was divorcing the 72-year-old.
Berlusconi has denied any scandal, saying Letizia is the daughter of an old friend from political circles and that he attended her birthday party because he happened to be in Naples that day. He has accused the center-left opposition of grabbing onto the gossip to try to discredit his party before European Parliament elections this weekend.
Berlusconi repeated Friday there was nothing "spicy" in his relations with Letizia and said he would resign immediately if someone could prove otherwise.
"If someone can demonstrate that the premier perjured himself, the premier would have to resign and hide himself the next minute," he told state-run RAI radio.
Letizia's ex-boyfriend has said Letizia and several other young women spent a week at Berlusconi's Sardinian villa over New Year's and that he listened in on phone calls between Berlusconi and Letizia, fueling speculation about an inappropriate relationship between the two.
Photographer Antonello Zappadu shot hundreds of photos of the party from outside the villa's gates - photos which were seized by Rome prosecutors last week at Berlusconi's request. But Zappadu said he had already sold the rights to the photos outside Italy, possibly explaining their publication by El Pais under the headline "The photos vetoed by Berlusconi."
One of the pictures features two topless women in the garden, another shows a naked man poolside, a third shows a woman in a red coat while two others show Berlusconi walking in the garden. Besides Berlusconi, all have their faces fuzzed over and none is identified.
Berlusconi's lawyer Niccolo Ghedini said he had retained a lawyer in Madrid to file a complaint against El Pais, charging they published photos that were linked to a crime.
"They are photographs that originated in a crime," Italian Web site www.affaritaliani.it quoted Ghedini as saying. "Who buys them anywhere in the world is committing a crime, something which should have been clear to El Pais' journalists." Ghedini's assistant, Piersilvio Cipollotti, confirmed the quotes.
Juan Cruz, a spokesman and senior journalist at El Pais, said the daily was unaware of any lawsuit and so could not comment.
"We published the photos in the public's interest. It's information and that's the way we treated it," he told The Associated Press in Madrid. "We believe what we did is journalism."
Berlusconi has denounced the paparazzi for what he has said was an invasion of his privacy - a charge he repeated Friday after El Pais published the photos.
"We're talking about innocent photos, but there was a violation of privacy," he told RAI.
Asked about why there were naked women at his home, Berlusconi continued: "Do you take a shower dressed? These girls were bathing in a Jacuzzi inside a private home, and they were assaulted in a scandalous way."
The photos have also sparked an investigation by Rome prosecutors into alleged abuse of office for the improper use of a government plane. Other photos show friends, entertainers and starlets arriving on a government plane in Sardinia for parties at the premier's home.
Berlusconi has said the guests were flown in at no extra cost to taxpayers to provide entertainment during a state visit by outgoing Czech Prime Minister Mirek Topolanek. He has said he was sure the case would be dismissed and denounced the probe as politically motivated.