By Crispian Balmer
ROME (Reuters) - Italy's Senate voted on Wednesday to block magistrates from using wiretaps as evidence against former Prime Minister Silvio Berlusconi in a trial where he is accused of bribing women to keep quiet over his "bunga bunga" sex parties.
The secret vote sparked fury in parliament, with Prime Minister Matteo Renzi's ruling Democratic Party (PD) and the anti-establishment 5-Star Movement (M5S) blaming each other for saving Berlusconi from potential embarrassment in court.
M5S leaders said the centre-left PD had stepped in as part of a hidden pact to secure the backing of Berlusconi's centre-right Forza Italia party in future political battles.
Renzi supporters accused their opponents of framing them, saying M5S had saved the scandal-plagued Berlusconi to smear the government in a plot worthy of the wily Renaissance diplomat Niccolo Machiavelli.
"Dirty maneuvering by the Five Star has saved Berlusconi," said junior government minister Luciano Pizzetti. "They talk about morality, but they operate in the shadows."
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Berlusconi, who underwent major heart surgery last month, was acquitted last year of having sex with an under-aged prostitute at his parties. The judge ruled that it could not be proved that he knew the woman was just 17 at the time.
However, he was ordered to stand trial again, this time accused of handing out some 10 million euros ($11 million) to persuade his guests to keep quiet about his revelries.
Berlusconi, ousted as prime minister in 2011 in the midst of the euro zone financial crisis, has denied the accusations.
Part of the case is based on phone taps carried out in 2012 when Berlusconi was still a parliamentarian. As such, prosecutors needed the Senate's approval to bring the evidence to court. Their request was turned down by 130 votes to 120.
The recordings can still be used, but only against some of Berlusconi's 30 co-defendants, who have been accused of accepting bribes or facilitating corruption.
Wednesday's secret vote came at a time of growing political tension in Italy. The M5S IS overtaking the PD in the polls and Renzi has promised to stand down if he loses a referendum in October or November on his constitutional reform drive.
The comedian Beppe Grillo, who founded M5S, said the Senate ballot was connected to the forthcoming reform ballot.
"Now that the constitutional reform is getting close, the PD has saved Silvio in exchange for benevolence, both on his part and the part of his powerful media empire," Grillo said.
Berlusconi has some 40 senators in the 315-seat upper house and needed substantial outside backing to head off the magistrates. His party welcomed the vote, but did not speculate who might have ridden to his defence.
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(Reporting by Crispian Balmer, editing by Larry King)