(By Kate Carlisle) Rome, July 18 - The centre-right People of Freedom (PdL) party released an elaborate document on Thursday accusing 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 was upheld by an appeals court in May, and the supreme Cassation Court will hear his appeal on July 30. It also includes a five-year ban from public office for the ex-premier that would kick in if parliament ratifies it. 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 savings 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. In May Italy's supreme Court of Cassation said that claims of bias by Milan judges made by Berlusconi were "defamatory accusations" after rejecting the media magnate's petition for a sex trial and for the appeal against the four-year conviction for fraud to be transferred to Brescia. Following the July 10 decision by the Cassation to set the date it will hear the Mediaset case for the end of the month, Berlusconi called on Italians to join him in public protests and sign a referendum for judicial reforms. "All of Italy needs to join together publicly, all around the country, to sign the referendum," Berlusconi said. The PdL has been particularly outraged over the Cassation's decision to rapidly schedule the appeal date, supposedly depriving his legal team enough time to prepare. Berlusconi's defense team have called the move "beyond logic". The Cassation said it was forced to move on the case or there was a risk part of the conviction would be timed 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 the verdict against their leader is upheld in appeals. Three years of the four-year sentence would not have to be served because of an amnesty. Berlusconi would not have to serve the remaining year in prison if definitively convicted since he is over 70, though he would have to do social work. 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. The tax-fraud case is the most immediate of Berlusconi's cases to come to a final conclusion. He is also appealing a seven-year sentence and life ban for paying an underage prostitute nicknamed Ruby for sex and a one-year term for involvement in the publication of a wiretap that hurt a political rival, while he may face trial for allegedly buying Senators to bring down a previous centre-left government. Berlusconi has always denied any wrongdoing.