Rome - Italy's former premier, Silvio Berlusconi, for the first time in decades of criminal prosecutions related to his media empire was definitively convicted of tax fraud and sentenced to prison by the nation's highest court.
Judge Antonio Esposito, in reading the court's decision on Thursday, declared Berlusconi's conviction and four-year prison term "irrevocable".
He also ordered another court to review the length of a ban on public office - the most incendiary element of the conviction because it threatens to interrupt, if not end, Berlusconi's political career.
The tensely awaited decision puts fresh pressure on Premier Enrico Letta's fragile coalition government, which relies on support from Berlusconi's forces and his own centre-left Democratic Party to pass reforms needed to restore market confidence in Italy and haul it out of recession.
Letta appealed for calm, issuing a statement saying that "for the good of the country it is necessary now that a climate of serenity prevails".
One of Berlusconi's top lawmakers pledged to stay true to their leader's promise to keep the party in the government.
"The ruling will not impact on the fate of the government," said Nitto Palma, emerging from a huddle of party leaders at Berlusconi's Rome residence. "We will continue to support this government." Berlusconi's aides said he planned to deliver a video statement.
Opposition lawmakers, however, were eager to describe the ruling as momentous.
"Berlusconi is dead," declared Beppe Grillo, the leader of the anti-establishment 5 Star Movement, on his blog. He compared the conviction to the fall of the Berlin Wall in 1989 that helped bring down Soviet communism.
Berlusconi's exit from the political scene he has dominated since the early 1990s is unlikely to be quiet. A Milan appeals court will now have to determine the length of a public office ban.
Lower courts had put it at five years, but a state prosecutor recommended in its arguments this week that it be lowed to three, citing conflicts in the relevant sentencing laws.
A long-time Berlusconi stalwart and one of his former ministers, Ignazio La Russa, called the ruling to recalculate the length of the ban a "consolation prize".
Once the political ban length has been decided, the Senate, where Berlusconi holds a seat, will have to debate and vote on revoking his seat as part of a process that can stretch for months, if not a year.
If the Senate opposes it and refuses to formally revoke Berlusconi's seat, the high court could turn to the constitutional court in a bid to resolve the standoff.
Berlusconi is highly unlikely to actually go to prison. Three years will be shaved off as part of a general pardon for crimes committed before 2006 aimed at easing prison crowding, and it is unusual for defendants to serve sentences of just one year for a first offense, particularly at Berlusconi's age, 76.
He would likely be given the choice to serve the remaining year under house confinement or opt for social services.
Berlusconi awaited the sentence at his residence in central Rome with his lawyers, deputy party leader Angelino Alfano and his eldest daughter, Marina, all of whom were seen entering the building in the hours leading up to the announcement. He issued no immediate reaction.
Thursday's court decision does not end Berlusconi's judicial woes. He was convicted in June of paying for sex with an under-age teen and then forcing public officials to cover it up. The court sentenced him to seven years in jail and a lifetime ban on public office, a ruling he is appealing.
A Naples court is also investigating him for allegedly bribing a lawmaker to bolt a previous centre-left government under Romano Prodi and join his party, a move that weakened Prodi's slim majority.