The anti-establishment 5-Star Movement (M5S), which is currently vying with Premier Paolo Gentiloni's Democratic Party (PD) to top the polls, and the rightwing Northern League and Brothers of Italy (FdI) parties both called for snap elections.
The same call was made by ex-premier Matteo Renzi, the PD secretary, who quit as head of government in December when his flagship Constitutional reform was rejected in a referendum.
Meanwhile, a rebel minority within Renzi's PD and Silvio Berlusconi's centre-right Forza Italia came out against early elections.
FI said parliament should now step in to harmonise the electoral systems of the two houses of parliament.
The Italicum was designed only to be used in the Lower House, as the Senate was meant to become an assembly of regional representatives under the rejected Constitutional reform.
One of Renzi's predecessors as PD leader, Pier Luigi Bersani, said it was not a good time to hold an election campaign given the country's problems, including reconstruction in areas of central Italy hit by the recent series of earthquakes.
"I won't take any election law because we have to vote," Mr Bersani told Italian daily Corriere della Sera.
"Elections are not the only thing; there are people's lives too."
On Wednesday the Constitutional Court ruled legitimate a winner's bonus in the Italicum awarded to any party getting more than 40 per cent of votes.
The top court declared illegitimate, however, a part of the Italicum allowing a party list head elected in more than one constituency to choose the constituency he wanted to represent.
It also said a run-off envisaged in the Italicum if no party reached the 40 per cent threshold was illegitimate.
With ANSA
