ROME - Italy's political gridlock deepened on Wednesday with bickering between the main leftist party and a new anti-establishment party putting off the prospect of a new government any time soon, following shock elections that have spooked Europe.

Comedian turned populist firebrand Beppe Grillo said his Five Star Movement (M5S) would not endorse the Democratic Party (PD), which won the most votes in the elections on Sunday and Monday but not enough to

form a majority in parliament.

"The M5S is not going to give a vote of confidence to the Democratic Party or to anyone else," Grillo, who has channelled the frustrations of austerity-weary Italians, wrote on his blog.

The comment appeared to be a rejection of overtures from the PD, which on Tuesday held out the possibility of working with M5S on key reforms like slashing government costs and helping Italy's poorest get through a grinding recession.

Grillo said the PD had made a series of "indecent proposals", prompting PD leader Pier Luigi Bersani to hit back with a statement saying: "If Grillo has something to say to me, including the insults, I want to hear it in parliament."

Grillo has railed against traditional politicians and has called for a referendum on the euro. His party won 163 seats in the lower and upper houses.

After market panic on Tuesday, investors were more measured on Wednesday, especially after a better-than-expected bond sale even though Italy's borrowing costs spiked.

European capitals remained nervous however amid fears Italy could turn back the clock on reforms and austerity following an election that had been seen as crucial for the future of the eurozone.

Italian President Giorgio Napolitano on Wednesday cancelled planned talks with the man bidding to unseat German Chancellor Angela Merkel after he called two Italian political players "clowns."

Commenting on the inconclusive vote in Italy, Steinbrueck said late Tuesday he was "downright appalled that two clowns won" a reference to the big votes won by showman Grillo and scandal-tainted former premier Silvio Berlusconi.

Government officials such as Foreign Minister Guido Westerwelle have called on Italy to continue on the path of reform pursued by outgoing Prime Minister Mario Monti that led to improved confidence in the financial markets.