By James Mackenzie
ROME (Reuters) - Italian Prime Minister Enrico Letta dismissed signs of growing tension in his government on Tuesday, ahead of a confidence vote next week to confirm his new majority after Silvio Berlusconi's Forza Italia party quit the ruling coalition.
The government said the vote would be held on December 11, after Letta's center-left Democratic Party (PD) elects a new leader this coming Sunday.
He gave no details on new policy proposals but said a limited program of institutional and economic reforms would be agreed with coalition partners, including Angelino Alfano, the leader of the small center-right group that broke away from Berlusconi and supports the government.
The decision comes a week after Letta won a Senate confidence vote on the 2014 budget by 171 votes to 135, despite Forza Italia's vote against the coalition.
Although Letta's majority appears solid enough to ensure he wins the vote, he must deal with growing tensions between members of his coalition government, now dominated by his PD.
Matteo Renzi, the ambitious young mayor of Florence who appears set to win the PD party leadership on Sunday, has demanded that the center-left put its stamp more clearly on the coalition, prompting an angry reaction from the center-right.
With Berlusconi out of parliament over a tax fraud conviction, Renzi's ambitions have drawn accusations that he could be tempted to push for early elections to profit from divisions in the center-right.
However Letta said he was "absolutely convinced" that whoever wins the center-left election would back the government.
"I have no doubt that the PD secretary who is elected on Sunday will be a fundamental factor in ensuring the stability of this government," he said at an event on Tuesday.
Formed after February's deadlocked election, which left no side able to govern alone, Letta's unwieldy coalition with Berlusconi struggled to overcome mistrust between the parties and passed few of the institutional reforms it had promised.
In a formal step to mark the change from the previous coalition, the lower house will vote on the confidence motion on the morning of December 11, followed by a vote in the Senate in the afternoon, the ministry for relations with parliament said.
Following last week's victory in the budget vote, Letta said his majority, although smaller, was more compact and effective. But the likely election of Renzi as PD leader could yet undermine that cohesion.
The challenge to the government was underlined on Tuesday by comments from European Monetary Affairs Commissioner Olli Rehn, who said Italy was not doing enough to reduce its huge public debt, the second highest in the euro zone. It is set to top 133 percent of gross domestic product this year.
Letta gave a sharp rebuff to Rehn, saying it was not his place to express skepticism over Italy's budget plans. He said Italy's accounts were in order and it was vital not to stifle early signs of growth with too much austerity.
Parliament has still not passed the 2014 budget amid wrangling over such as issues as financing the replacement of a hated housing tax, a key demand of the center-right, while respecting European Union borrowing limits.
The government must also tackle the intractable issue of reforming a voting system blamed for the stalemate created by the last election.
All sides agree the election law, which makes it difficult for any side to gain a working parliamentary majority, must change, but the parties have failed to agree on an alternative.
(Editing by Robin Pomeroy)