By Roberto Landucci
ROME (Reuters) - Prime Minister Matteo Renzi's plans to slash the powers of Italy's Senate, a key element of his reform agenda, have run into trouble, with opposition politicians submitting nearly 8,000 amendments to delay its approval.
The plans to reduce the upper house Senate to a small chamber made up largely of local politicians and stripped of its power to pass most national laws or hold votes of no-confidence in the government are intended to streamline lawmaking and avoid a repetition of the deadlock after last year's election.
Under Italy's current system, both houses of parliament have almost exactly equal powers but are elected under separate rules that make it difficult for one party to secure an overall majority in the two chambers.
On Thursday, the president of the Senate, Pietro Grasso, curtailed the debates in a bid to force through a first reading of the bill by Aug. 8, prompting furious protests from the anti-establishment 5-Star Movement and the Northern League.
Dozens of opposition lawmakers marched to the Quirinal Palace to lodge their protest with President Giorgio Napolitano.
Maria Elena Boschi, the minister for reforms who is piloting the bill through parliament, said opposition parties' obstruction had forced drastic action after only five amendments were passed in three days of debate.
"Either they substantially withdraw the amendments or we'll go ahead (with the 'guillotine' curtailing debate) because you can't have a discussion like this," she said.
Renzi has secured the backing of ex-prime minister Silvio Berlusconi's center-right party but has faced growing opposition from other groups who say the changes will undermine parliament and remove effective checks on government power.
Attempts at dialogue have proved largely fruitless. Renzi repeated his determination on Thursday to continue with the reform, which still faces at least three further readings in parliament and may also become subject to a referendum.
"Whether they like it or not, we're going to do the reforms," he said in an interview on Italy's La7 television.
The resistance to the plans threatens to undermine Renzi's longer-term aim of implementing a substantial program of reforms within the next three years to revive Italy's stricken economy and cut its record unemployment.
Already there has been talk in Renzi's center-left Democratic Party that the 39-year-old prime minister could be forced to call a snap election if the Senate reforms and a separate change to the electoral law are delayed.
As well as reform of parliament, the government has promised to overhaul the notoriously costly and inefficient public administration, cut back overlapping levels of regional government and reform the justice system to improve the basic functioning of the Italian state.
It also faces testing battles to make employment law more efficient and to reduce the power of entrenched lobby groups ranging from lawyers to pharmacists.
At the same time, Italy's economic outlook has continued to darken and Renzi said on Thursday it would be "very difficult" to reach the official target of 0.8 percent growth in 2014.
Other groups, including the Bank of Italy and business association Confindustria, have cut their estimates for the year to near zero growth, a result which would make it more difficult to meet European Union borrowing limits and to control a public debt likely to top 135 percent of national output this year.
(Writing by James Mackenzie; Editing by Gareth Jones)