By Gavin Jones
ROME (Reuters) - A small Italian centrist movement said on Wednesday it was quitting the ruling majority, dealing a further setback to Prime Minister Matteo Renzi after a weaker-than-expected showing by his Democratic Party (PD) in weekend local elections.
The Popolari Per l'Italia group, led by former Defence Minister Mario Mauro, said it could no longer support Renzi's "improvised and sloppily conducted" reforms which were holding back Italy's economy.
The group has only a small presence in parliament but in the Senate, the upper house where Renzi has a slim and unstable majority, any defections can create potential obstacles to pushing through legislation.
The party has three senators but one is more sympathetic to Renzi and said she would not follow Mauro and would remain in the majority.
Mauro comes from Italy's centre-right and was defence minister under Renzi's predecessor, Enrico Letta.
He has been critical of Renzi's education reform currently before parliament and also of his changes to the electoral law.
The education reform gives more power to school directors to hire and promote staff while the electoral reform aims to ensure a clear winner at elections by giving a big winner's bonus of seats in parliament to the largest party.
The regional ballot saddled Renzi with his first electoral reverse since he took office in February 2014 after ousting Letta in an internal party coup.
His PD won in five of the seven regions at stake but its support declined steeply from a triumph at European elections a year ago, threatening to deepen opposition to Renzi from PD left-wingers.
Candidates chosen by Renzi fared particularly badly, suffering bruising defeats in the northern regions of Veneto and Liguria, while those that fared better mainly came from the party's old guard.
With tensions in the PD rising almost daily, comments by Renzi after the election that he planned to accelerate the "renewal" of his party were widely seen as an ominous sign for his internal critics.
The PD executive will meet on Monday of next week to analyse the election result.
Renzi is determined to impose greater cohesion in the party ahead of potentially bruising parliamentary battles over his education reform and plans to overhaul the public administration and abolish the Senate as an elected chamber.
In Liguria, the presence of a breakaway candidate backed by former PD left-wingers contributed to the centre-left's defeat, and the prospect of more PD defections are seen a growing risk for the premier.
(Additional reporting by Paolo Biondi; Editing by Mark Heinrich)
