Luigi Di Maio, leader of the populist Five-Star Movement - Italy's biggest parliamentary party - on Monday ruled out any prospect of governing with former premier Silvio Berlusconi and the centre-right alliance.
"There is a 0% chance of the Five-Star Movement entering government with Berlusconi and his collection of centre-right parties," tweeted Di Maio.
The tweet came after Matteo Salvini, leader of the far-right League party, which heads the centre-right coalition, said he would only negotiate with Five-Star on forming a government, shunning any coalition with the centre-left Democratic Party.
The centre-right coalition which includes Berlusconi's conservative Forza Italia party, emerged as the largest group after Italy's inconclusive 4 March national election led to a hung parliament.
The Democratic Party (PD) came third in the polls - its worst-ever electoral result and Salvini has rejected any coalition with the PD which has so far vowed to go into opposition.
Italy's president Sergio Mattarella last week held two days of formal talks with Italy's main party leaders which failed to break the political deadlock and is due to hold fresh talks later this week.
Both Five-Star and the League are laying claim to a first bid to form a government.
Salvini has refused to break with Berlusconi, which is a condition posed by Five-Star leader Luigi Di Maio for a tie-up.
Berlusconi has made clear he wanted nothing to do with Five-Star, in response to its own rejection of him due to his tax fraud conviction.
The complex web of apparently irreconcilable demands have complicated Italian president Sergio Mattarella's talks with party leaders and his advisers have warned that it could take many weeks to find a solution.
But Mattarella is keen to avoid fresh polls this year and wants to have a coalition government in place by a European Union heads of state and government summit taking place in Brussels on 28 June, La Repubblica daily reported on Monday.
