President Mattarella to begin crisis consultations with political leaders on 8 December.

Matteo Renzi has resigned as prime minister of Italy, making good on his promise to step down in the event of defeat in the 4 December referendum on a controversial government-backed constitutional reform.

Renzi handed in his resignation to President Sergio Mattarella on the evening of 7 December, shortly after the senate definitively approved the 2017 budget law.

Mattarella did however ask the executive to continue tending to ordinary business while he seeks a solution to what is shaping up to be a complicated government crisis.

Crisis consultations are set to begin at 18.00 on Thursday, when the head of state will meet with the speakers of the senate and chamber of deputies, Pietro Grasso and Laura Boldrini, and former president of the republic Giorgio Napolitano.

On Friday and Saturday Mattarella will then meet with representatives of all political parties, concluding with the biggest parties – the right-wing and anti-European Lega Nord, the centre-right Forza Italia led by ex premier Silvio Berlusconi, the anti-establishment Movimento Cinque Stelle (M5S) and Renzi’s own Partito Democratico (PD).

At a meeting of the PD party executive before tendering his resignation Renzi – who is also the party’s secretary – said he was not afraid of going to early elections once the constitutional court has handed down a ruling on a controversial 2015 electoral law known as the Italicum on 24 January.

In that event the country would vote under the terms of two different electoral laws: the Italicum as revised by the constitutional court for the chamber of deputies; and the old electoral law, known as the Porcellum for the senate, as revised by the constitutional court in a 2014 sentence (the revised law is commonly referred to as the Consultellum).

However, Renzi also said the other option would be to form a broad unity government to steer the country through until the natural end of parliament in 2018 in order to meet key international challenges and engagements next year.

A government of ‘national responsibility’ would presumably then have the task of pushing through new electoral reform, among other things.

Renzi suggested to the PD executive that he will not be part of the PD delegation that will meet with Mattarella to discuss the options on Saturday.

He also said that a “transparent” discussion of the referendum results will take place only after the government crisis has been resolved.

Meanwhile, the anti-establishment Movimento Cinque Stelle (M5S) has presented a bill in the chamber of deputies extending the principles of the Italicum electoral law to the senate.

The Italicum introduces a two-round system of voting for the chamber of deputies based on proportional representation, with a 40 per cent threshold at the first round and a majority premium for the winning party list.

The M5S has long been trying to style itself as an alternative to the PD and now wants to cash in on recent successes in local elections and particularly in the constitutional referendum to push for early elections, which under the present system of voting it could feasibly win.