ROME (Reuters) - Italy's center-left Democratic Party has slightly increased its opinion poll lead, according to a survey conducted just before a political crisis threatened to end Prime Minister Mario Monti's term early.
Elections are expected to be held early next year,
The poll by the SWG institute for RAI television showed the Democratic Party (PD) on 30.3 percent, up from 30 percent a week earlier, ahead of the anti-establishment 5-Star Movement of comic Beppe Grillo on 19.7 percent.
Silvio Berlusconi's center-right PDL party, which triggered instability on Thursday by withholding its support for Monti's technocrat government in two parliamentary confidence votes, saw a slight drop to 13.8 percent from 14.3 percent a week earlier.
The poll suggests that the PD would be the largest party in parliament but it would have to seek allies from smaller leftist or centrist parties to be able to form a government.
The poll of 1,100 people was taken between Monday and Wednesday this week, before Thursday's events in parliament which may force the election to be brought forward slightly.
The date of the vote remains uncertain pending a decision by President Giorgio Napolitano although Italy had in any case been expected to go to the polls no later than March.
The poll gave Monti an approval rating of 33 percent, a fall of three points from a week earlier to the lowest level since the former European Commissioner was appointed just over a year ago to succeed Berlusconi at the height of the financial crisis.
Monti, who has been credited with restoring Italy's credibility with financial markets but who has angered voters with a series of tax hikes and spending cuts, has said he would be available to serve a second term if the election fails to produce a clear winner.
He has previously said he would not run himself but there has been speculation that he may stand as a candidate.
A new centrist group headed by Ferrari chairman Luca Cordero di Montezemolo and seen as a possible vehicle for a Monti candidacy, saw its already slim support decline further, dropping to 2.4 percent from 3.8 percent.
(Reporting by Naomi O'Leary. Editing by Jeremy Gaunt.)