Rome, July 18 - The centre-right People of Freedom (PdL) party on Thursday accused Milan judges of partisan bias in their tax-fraud ruling against their leader, three-time premier Silvio Berlusconi. Berlusconi's four-year term for inflating film-rights purchases at his Mediaset media empire, cut to one for an amnesty, as well as a five-year ban from public office was upheld by an appeals court in May, and the supreme Cassation Court will hear his appeal on July 30. In a statement, the PdL said the series of trials was based on "an accusation so absurd and laughable that, in the presence of judges who are not totally compromised and non-partisan, (the trials) would be over before they begin, with a great saving of time for the judiciary and money for taxpayers". In its estimate, the PdL said his Mediaset trials have cost the State 20 million euros, "with the sole purpose of condemning an ideological and political enemy, Silvio Berlusconi". Berlusconi and his supporters have repeatedly accused Italian judges of "political persecution," prompting implicit rebuke from the judiciary's self-governing body and its titular head Giorgio Napolitano, the Italian president. The PdL has been particularly outraged over the Cassation's decision to hear his case allegedly so soon at the end of this month, supposedly depriving his legal team enough time to prepare. The Cassation said it was forced to move on the case or risk it timing out under the statute of limitations, something that has happened a number of times in the media mogul's previous legal entanglements. PdL lawmakers have vowed to resign en masse if their leader's ban from office is upheld. The threats have added tension to an already unstable coalition government, cobbled together from the center left and center right after two months of post-election parliamentary gridlock earlier this year.