Italy's centre left leader Pier Luigi Bersani has said his attempts to form a government have failed.

"I told the president that negotiations haven't led to a positive outcome," a worn-out Bersani told journalists at the end of a meeting with Italian president Giorgio Napolitano at the Quirinale Palace in Rome.

Napolitano had given Bersani the mandate to try to form a government following inconclusive election results in February.

Bersani has been holding talks with his political rivals to cobble together a compromise to find the parliamentary majority necessary for a government to be installed.

But "difficulties and unacceptable conditions" brought up by the other parties caused negotiations to fail, Bersani said.

His leftwing coalition won a majority of seats in the lower chamber of parliament but is 35 seats short of a majority in the upper house and needs the backing of senators from Beppe Grillo's M5S or Silvio Berlusconi's People of Freedom party (PDL) to form an administration.

Bersani ruled out a coalition with Berlusconi's centre-right coalition as "neither viable nor credible".

But his repeated attempts to convince at least some of M5S's MPs to support him failed badly.

Talks between Bersani and M5S representatives Vito Crimi and Roberta Lombardi were streamed live on Grillo's blog.

"Only a mentally ill person could have an itching desire to govern right now," Bersani told Crimi and Lombardi. "I'm ready to listen and take on the responsibility."

Crimi replied M5S could not back a Bersani-led government because he had lost credibility during his 20 years as a politician.

After the meeting Grillo called Bersani a "whoremonger" on his blog.

Napolitano is now likely to give a similar mandate to a candidate who has more credibility among party leaders.

If the political gridlock is not resolved, Italy will have to hold a new election - but not before a new president is appointed by parliament as Napolitano's terms ends on May 15.