In an online statement jointly signed with Gianroberto Casaleggio, cofounder of the Five Star Movement (M5S), Grillo gave the prime minister a 24-hour time limit to respond to his demands.
“Weeks ago we gave our availability to meet [to talk] about the electoral law...it’s necessary to conclude this debate as soon as possible,” the M5S leader said.
“If a meeting date with our delegation during the week is not confirmed, together with points to our responses, we will take action and leave negotiations...We await a response within the next 24 hours,” Grillo concluded.
His statement comes after a meeting between the M5S and Renzi’s Democratic Party (PD) was cancelled last Monday, with both sides blaming each other for the stalling of negotiations.
Overhauling Italy’s electoral system has been a key part of Renzi’s reform package and is a legal necessity, after the country’s courts in December ruled the current process unconstitutional. The current law is widely blamed for the political stalemate which followed the February 2013 elections, in which no party won an outright majority.
Before taking power in February this year, Renzi met with opposition leader Silvio Berlusconi to negotiate a new electoral law and win the backing of the former premier’s Forza Italia party.
Grillo until recently stayed away from the reform process, instead adopting a firm anti-establishment stance and criticizing the meeting between Berlusconi and Renzi.
But he has changed tack in recent weeks, after the European elections saw the PD winning 40.1 percent of the vote and a significant gain over the M5S.