Italy's supreme court has upheld a prison sentence given to former PM Silvio Berlusconi for tax fraud. When he was convicted last October, he was sentenced to four years in prison but this was automatically reduced to a year under a 2006 pardon law. Berlusconi faces house arrest or community service instead of going to jail because of his age - he is 76. However, the court ordered a review of a five-year ban on public office that was part of the original sentence. It is the billionaire businessman's first definitive conviction in up to 30 court cases on a variety of charges. The ruling by Rome's Court of Cassation came after a three-day hearing. The judicial review of the five-year ban from public office will enable Berlusconi to remain as a senator and as leader of his centre-right People of Freedom Party (PDL) for now. The BBC's Alan Johnston in Rome says it is a devastating judgement against the former prime minister, although he will be relieved that judges ordered a review of the political ban. Berlusconi's party is one half of Italy's coalition government: Prime Minister Enrico Letta needs both the PDL and his own centre-left Democratic Party to govern. Italian President Giorgio Napolitano issued a statement after the court ruling, urging the country to stay calm. "The country needs to rediscover serenity and cohesion on vitally important institutional matters which have for too long seen it divided and unable to enact reforms," he said. The original ruling said that Berlusconi's Mediaset media empire had inflated the price it had paid for film distribution rights to avoid paying taxes. He was labelled the "author of a whole system of tax fraud". 'Vendetta' The three-time prime minister and senator has faced a string of trials since leaving office in November 2011. Appeals are pending in other cases in which he was convicted of having paid for sex with an underage prostitute, and arranging for a police wiretap to be leaked and published in a newspaper. Two other alleged tax evasion cases, one of them involving British lawyer David Mills, expired under the statute of limitations. Berlusconi accuses magistrates from his home city of Milan of pursuing a "vendetta" against him.