ROME: Surprise victories for Italy's centre-left in securing the posts of speaker in both houses of parliament have done little to unblock a political impasse which threatens to create renewed instability in the eurozone.

"The main issue -- the existence of a governing majority -- remains a puzzle without a solution," said left-wing daily La Repubblica.

Italy's new parliament on Saturday elected a former UN human rights official, Laura Boldrini, as speaker of the lower house.

Boldrini, 51, entered parliament for the small Left, Ecology and Freedom party in a centre-left coalition that failed to win an overall majority in elections on February 24-25.

While Boldrini's election was widely expected, the upper house made a surprise decision to elect Pietro Grasso, the former head of Italy's anti-mafia agency who put hundreds of mafia members in jail as a judge before joining parliament this year as a senator for the main centre-left Democratic Party (PD).

Since Grasso attracted 12 votes more than there are lawmakers in the centre-left coalition, he had to have picked up votes from the new force in Italian politics, the anti-austerity Five Star Movement, which finished third behind former premier Silvio Berlusconi's centre-right coalition in the election.

The leader of the centre-left coalition, Pier Luigi Bersani, has for days been wooing the Five Star Movement, whose support he needs to form a government, but whose leader Beppe Grillo has bluntly refused to do business with him.

As a result, the eurozone's third-largest economy remains in limbo.

The left is still short of the absolute majority in the Senate it needs to win the vote of confidence that would lead to the formation of a government -- in Italy the two houses of parliament have equal legislative weight.

The ball is now in the court of 87-year-old President Giorgio Napolitano, who is due to begin meeting party leaders on Wednesday with a view to forming a government and ending the impasse.

"We are in a difficult period," Napolitano admitted in a televised address on Sunday to mark Italy's National Unity Day. He also met the newly appointed speakers of both houses.

"The biggest obstacle to the president baptising a new government is still the same -- there is no stable majority" in the Senate, said a commentator in the Corriere della Sera daily.

"The 12 extra votes obtained by Grasso in the Senate (thanks to the free spirits of a few of Grillo's supporters) do not change the PD's isolation and do not show that Bersani can form an alliance with the Five Star Movement and secure the majority in the upper house that he does not have at the moment," he added.

Napolitano is left with two main choices, according to La Repubblica commentator Franceso Bei.

Either he gives Bersani a mandate to form a government and takes the risk that it is defeated in a vote of confidence in the Senate, or he names a transitional government led by the head of the Bank of Italy, Fabrizio Saccomanni.

In the meantime, the outgoing technocrat government led by Mario Monti is left to take care of the country's day-to-day business.