Former Italian prime minster Silvio Berlusconi was handed a seven-year jail sentence for abuse of office and paying for sex with a minor.
He will not have to serve any jail time before he has exhausted an appeals process that could take years.
The conviction angered members of his centre-right party who questioned whether he should continue to support the coalition.
The 76-year-old media tycoon expressed outrage at the verdict which he said was politically motivated.
"An incredible sentence has been issued of a violence never seen or heard of before, to try to eliminate me from the political life of this country," Berlusconi said.
"Yet again I intend to resist against this persecution because I am absolutely innocent and I don't want in any way to abandon my battle to make Italy a country that is truly free and just."
Berlusconi's lawyers announced they would appeal against the ruling that also banned him from holding public office.
Berlusconi was found guilty of paying for sex with former teenage nightclub dancer Karima El Mahroug, better known under her stage name "Ruby the Heartstealer", during "bunga bunga" sex parties at his palatial home near Milan.
The panel of three women judges also convicted him of abuse of office by arranging to have El Mahroug released from police custody when she was held in a separate theft case.
The verdict closes a two-year trial that has mesmerised Italy with its accounts of wild sex parties at the billionaire's villa outside Milan while he was premier in 2010.
Several members of Berlusconi's People of Freedom (PDL) party have urged him to withdraw his backing for the government of centre-left Prime Minister Enrico Letta, which needs the PDL's support.
Berlusconi says the purported sex parties were elegant dinners where the female guests performed "burlesque" shows. Ms El Mahroug denied having sex with Berlusconi.
In the verdict, the judges said around 30 witnesses in the case, including Deputy Foreign Minister Bruno Archi, should be investigated for perjury for their testimony in favour of Berlusconi.
In May 2010, the then-prime minister called a Milan police station to instruct officials to release Ms El Mahroug, who was being held on suspicion of stealing a €3,000 bracelet.
A Brazilian prostitute who lived with Ms El Mahroug had called the premier on his mobile phone to tell him she had been arrested, prosecutors said.
Berlusconi's lawyers have said he made the call to avoid a diplomatic incident because he believed that Ms El Mahroug, who is actually Moroccan, was the grand-daughter of Hosni Mubarak, then the Egyptian president.
The prosecution said he was anxious to cover up the relations he had with her at his sex parties.
The media magnate has recently used his own television stations to promote his version of events, with his flagship Canale 5 channel broadcasting a prime-time documentary on the so-called "Ruby Trial".
The verdict is only part of Berlusconi's legal problems.
Last month an appeals court upheld a four-year jail sentence against him for orchestrating a tax fraud scheme in his business dealings - leaving him just one more appeal, at the Supreme Court, which could come within a year.