* Centre-left leader outlines 8-point "core programme"
* To seek parliament approval, rejects deal with Berlusconi
* Calls on Grillo to act responsibly
By James Mackenzie
ROME, March 6 (Reuters) - Italian centre-left leader Pier Luigi Bersani, under fire for falling short in last week's election, sought on Wednesday to rally his party behind a plan to form a minority government backed by populist leader Beppe Grillo.
Bersani, whose coalition threw away a 10-point lead in the opinion polls before the Feb. 24-25 vote, won control of the lower house but let slip a workable parliamentary majority by failing to win the Senate.
The result has left no group able to form a government on its own and Italy facing weeks of uncertainty. A new election could be called within months if no accord can be reached between the divided parties.
In an address to officials of his Democratic Party in Rome, Bersani, a 61-year-old former industry minister, acknowledged that the result was a defeat but said the left was the only political force capable of forming a government.
"We are ready, if called on, to propose a government of change based on a core programme," he said. "Its purpose will be to open the way forward for parliament."
Bersani outlined an 8-point platform to be brought before parliament, ranging from stimulating growth in Italy's stagnant economy to cutting bureaucracy and cracking down on corruption.
He ruled out any agreement with centre-right leader Silvio Berlusconi, whose scandal-tainted government fell at the height of the euro zone debt crisis in 2011, saying a deal would be neither "credible nor feasible".
Behind his refusal to ally with Berlusconi lies an uncertain calculation which leaves Bersani dependent on the unpredictable Grillo, whose rebel 5-Star Movement was the big winner in the election with more than 25 percent of the vote.
Bersani said it was up to the ex-comic, who has ruled out both formal alliances and backing for any government in a confidence vote, to show whether he was prepared to act responsibly.
"Someone who obtained 8 million votes and who chose to go into parliament, not remain outside it, has to say what he wants to do for Italy with these votes," he said.
Parliament sits for the first time on March 15, after which President Giorgio Napolitano is expected to begin formal consultations with party leaders on March 19 to assess whether a government can be formed.
Without a vote of confidence, no government could function, so it is unclear how Bersani could form even a minority administration unless Grillo reverses his refusal to give formal assent.
Bersani won support from most party leaders speaking at the meeting but he is under increasing pressure over the election setback, with 38-year-old Florence mayor Matteo Renzi seen as the most likely successor in the longer term.
Bersani has been widely criticised for the centre-left's uninspired campaign, which failed to match either Berlusconi's political flair or Grillo's ability to tap into public anger at the waste and corruption in much of the political system.
Renzi has pledged his loyalty to Bersani, who beat him in last year's centre-left primary to choose an election candidate, but he said on Tuesday he would stand again in the future. He left Wednesday's meeting early without speaking.
"Bersani has given us a compass to navigate the crisis, which will be very complicated," former Prime Minister Massimo D'Alema told the meeting.
However in a sign of the tensions within the party, he warned against rejecting the centre-right as Bersani has done.
"The right exists," he said. "I regret the fact that at such a dramatic moment it is not possible in this country to respond with national unity."
A formal vote is expected after Bersani speaks again at around 6 p.m. (1700 GMT).
Although Grillo has ruled out supporting Bersani in a confidence vote, the centre-left's programme contains many points which could win support from the 5-Star Movement, which rode a wave of anger against the austerity policies imposed by Prime Minister Mario Monti's technocrat government.
Bersani proposed moving away from "the cage of austerity" and said he would lead a "correction to European stability policies" which had created a level of hardship that was putting the future of democracy at risk.
He also promised a range of policies to help those hit by Italy's longest recession in 20 years, as well as tough anti-corruption measures and an attack on bureaucracy and waste in the bloated political system.