Silvio Berlusconi has withdrawn his support for Italy's ruling coalition in a widely expected move on the eve of a vote to expel the billionaire tycoon from the Senate.
"The conditions for continuing our cooperation with this government no longer exist," said Paolo Romani, chief senator for Berlusconi's newly-revamped Forza Italia (Go Italy) party, calling on Letta to step down.
Letta "should draw his conclusions", Romani said.
"The grand coalition has finished today. One chapter is closing and another is beginning."
The move will not bring down Italy's left-right government since a group of former Berlusconi loyalists that broke away from the scandal-tainted ex-premier to form their own party have said they will stay in the coalition.
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The New Centre-Right group led by a former Berlusconi protege, Deputy Prime Minister Angelino Alfano, vowed to support centre-left Prime Minister Enrico Letta's coalition even if Berlusconi is expelled.
But Letta's government will now have a much slimmer Senate majority of around 10 senators, while it will continue to enjoy strong support in the lower house because of the presence of many centre-left politicians.
Alfano's party accounts for about 50 parliamentarians, but the precise numbers will become clearer in a key vote on next year's draft budget later on Tuesday.
Berlusconi's lawyers, meanwhile, played down the risk of the three-time former prime minister's arrest once his parliamentary immunity is withdrawn - a source of constant rumours in the Italian press.
"In theory, a prosecutor could ask for this measure but given Berlusconi's current situation we consider this idea absolutely unrealistic," Franco Coppi said.
But Berlusconi himself told an interviewer on Tuesday that prosecutors in Naples and Milan were "competing to see who gets me first".
