ROME (Reuters) - Italian centre-right leader Silvio Berlusconi on Saturday demanded a renegotiation of a reform of the upper house of parliament to which Prime Minister Matteo Renzi has tied his political future.
Renzi, 39, has vowed to quit if parliament blocks the reform of the Senate, part of a wider drive to slim down Italy's political apparatus and fix an electoral system blamed for creating deadlock and unstable governments.
Berlusconi had previously said his centre-right Forza Italia party would back the package, whose outlines he agreed with Renzi in January.
If Forza Italia were to oppose the measure, Renzi's coalition with the New Centre Right party and other smaller groups would still have a theoretical majority in the Senate of 169 votes to 139.
But Forza Italia's 60 votes could yet prove crucial if many government senators choose to defy a party line that calls for them to scrap their own jobs.
In a telephone address to a party event shortly after being released from hospital treatment for a knee problem, Berlusconi called the Senate bill "absolutely unacceptable" and appeared to withdraw his support altogether.
However, he later issued a statement in which he said his criticisms "refer to the composition" of the law, that Forza Italia still supported the aim of reforming the Senate, and that the party was willing to discuss "every detail" of the bill.
The deputy secretary of Renzi's Democratic Party, Lorenzo Guerini, blamed the turnaround on disagreements within Forza Italia and said the basis of the agreement still held.
"The Democratic Party will not get involved with internal arguments in Forza Italia, and remains calm and confident on the course of the reforms," Guerini said in a statement. "We are certain that the Senate agreement founded on four points stands ... the rest we can discuss in parliament with everyone."
The bill to transform the Senate into an unelected regional chamber is intended to create more stable administrations by removing the power of the upper house to approve budgets or hold votes of no confidence in a government.
Renzi had said he planned to get preliminary approval for the plan before European parliamentary elections on May 25.
The first step of his ambitious reform plan, to cut wasteful layers of local administration, was passed this week after the government made the measure a confidence vote.
(Reporting by Naomi O'Leary)