There was uproar in the Italian Parliament today as Silvio Berlusconi, the centre-right Prime Minister, sought to push through a decree which the left-wing opposition said would save him from a possible prison sentence by suspending "non priority" trials for a year.

The proposal would freeze Mr Berlusconi's current corruption trial in Milan, in which he is charged with giving a $600,000 (£300,000) bribe to David Mills, his former tax lawyer and estranged husband of Tessa Jowell, the Olympics Minister, in exchange for giving allegedly misleading testimony in two corruption cases during the 1990s.

Both Mr Berlusconi and Mr Mills deny any wrongdoing. However the prosecution is finalising its case and the judge is expected to pass sentence soon.

The centre-left opposition tabled hundreds of protest amendments in the Senate in a filibustering move to sabotage the decree, which it dubbed a "Salva Premier" (Save the Prime Minister) measure. The decree must be passed by both houses of Parliament by 23 July - 60 days after it was issued - to become law.

If passed the decree, part of a wider "security package" on law and order, would suspend all trials for offences committed before 2002 except in the case of crimes punishable by a prison sentence of 10 years or more and those which involve violence, the Mafia or workplace accidents. Mr Berlusconi said this was intended to speed up Italy's notoriously slow and inefficient judicial process.

However Lanfranco Tenaglia, the Shadow Justice Minister, said it was really to do with "the Prime Minister's perennial conflict of legal interests". In a letter to Renato Schifani, the Senate President and a political ally, Mr Berlusconi admitted that "my lawyers have informed me that this measure would be applicable to one of a number of fanciful trials that far-left magistrates have brought against me for political reasons".

The decree would also guarantee immunity from prosecution for the holders of Italy's top five offices of state, including that of Prime Minister. Mr Berlusconi tried to pass such a measure in 2003 during his last term of office, but it was overturned by the Constitutional Court on the grounds that no-one is above the law.

In a further apparent move to delay the trial Mr Berlusconi's lawyers today asked for Nicoletta Gandus, the judge hearing the case, to be removed on the grounds that she was "openly hostile" to Mr Berlusconi.

Walter Veltroni, leader of the Opposition, who has been criticised for being too soft on the Berlusconi government since he was defeated in the April elections, warned that he could break off dialogue with Mr Berlusconi on constitutional reforms if the decree went through.

The security package also includes a proposal to put 2,500 troops on patrol in large cities alongside police, restrictions on magistrates' use of phone tapping in investigations and the expulsion of EU citizens unable to prove they have "sufficient economic resources" to stay in Italy for more than three months, a measure aimed above all at Romanians.

Journalists who published leaked testimony in preliminary investigations would be prosecuted. Italian newspapers frequently print leaked transcripts of interrogations and intercepted conversations in what amounts to "trial by media" as a substitute for judicial process.

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