Rome, February 27 - Anti-establishment Five Star Movement (M5S) chief Beppe Grillo on Wednesday rebuffed overtures from Democratic Party (PD) leader Pier Luigi Bersani aimed at achieving a majority in the deadlocked Senate and said the PD head should quit after squandering his coalition's big pre-election poll lead over ex-premier Silvio Berlusconi. Grillo called Bersani "a political stalker who has been bothering the M5S for days with indecent proposals instead of resigning like anyone else in his position would". Bersani responded by saying "whatever Grillo has to say to me he should tell me in parliament, and everyone should assume their responsibilities". The M5S rode a huge anti-austerity, anti-euro and anti-politics protest vote to become the biggest single party in the House and potentially the hinge force in the Senate, where no one got a majority, in the Sunday-Monday elections. Berlusconi, written off as dead a year ago, stormed back into the reckoning with a crowd-pleasing media blitz for his re-energized People of Freedom (PdL) party, almost making the election result a PD-PdL dead heat. The PD alliance with smaller leftist ally SEL scraped a House win with a 0.34% edge over the centre right and got two more Senate seats than the PdL-led forces. But Italy's controversial election law secured the centre left a 340-seat majority in the House, leading Bersani to take an initial run at a tricky government-forming task, although he has not yet received a formal mandate from President Giorgio Napolitano. On Tuesday Bersani appealed to Grillo to support a 5-6-point platform including political spending cuts, the abolition of provincial governments, a conflict-of-interest law and electoral reform, enabling a confidence vote that would break the Senate deadlock. The tub-thumping Genoese activist comic and potential kingmaker initially appeared to suggest this might work, along the lines of the PD-led Sicilian administration the M5S is supporting on an issue-by-issue basis, which Grillo called "miraculous". But on Wednesday he scoffed at Bersani's proposal, saying the M5S "will only vote for laws that reflect our platform". Amid widespread perceptions that the PD was the big loser Monday even though it narrowly came top in both houses, Bersani is facing calls from disappointed voters to stand down in favour of Florence Mayor Matteo Renzi, his defeated opponent in November primaries, who polls say has a broader appeal.