The Italian foreign minister and former leader of the Five Star Movement (M5S) is calling for protests this weekend against the government he sits in, as Italy appears set for another period of political instability.

Luigi Di Maio said the Italian people “must peacefully demonstrate” in Rome on Saturday against a system that “wants to cancel our laws”.

The uneasy coalition between the anti-establishment M5S and the centre-left Democratic party (PD) was formed last year to prevent elections that could have brought Matteo Salvini’s far-right League to power, but has been seriously weakened by dwindling support for M5S and a steady exodus of its elected representatives.

The appeal to protest was ramped after Matteo Renzi, the former prime minister who leads Italia Viva, a PD splinter group that is part of the government coalition, on Tuesday threatened a no-confidence vote on the M5S justice minister, Alfonso Bonafede, in a row over justice reforms.

M5S, founded by the comedian Beppe Grillo, was phenomenal in opposition, enabling it to come first in national elections in March 2018 with 33% of the vote. But it has been less successful at governing, with Salvini capitalising on the party’s inexperience to double support for the League while the two parties were in coalition.

M5S lost over half of its voters since 2018 with bruising defeats in recent regional elections in Emilia-Romagna and Calabria testament to just how bad things have become.

Jacopo Iacoboni, author of The Experiment, a book about M5S, said Di Maio’s call to protest was an attempt to remind the party of its earliest ideals.

Di Maio, who quit as party leader in January amid party turmoil, claims the government is planning to backtrack on a policy to reduce the pensions of former MPs. Curtailing parliamentary privileges was an M5S rallying cry and among the first policies approved during its short-lived alliance with the League.

He said the government is conspiring to abolish the universal basic income, another key M5S policy that was rolled out last year after a fierce budget battle with the EU.

“Di Maio is aiming to reaffirm that M5S remains strictly devoted to its main historical issues,” Iacoboni said. “By doing so, he is not helping his own government at all. However, the idea is not so much to produce a real crisis, but to make his people feel alive and what remains of M5S voters to feel comfortable with their own political history.”

Nicola Zingaretti, who leads PD, called Saturday’s protest “a mistake” and invited Di Maio to “look to the future”.

But nostalgia is motivating the 33-year-old as he tries to revive the angry spirit of a movement that drew swaths of supporters to Italy’s piazzas when it burst on to the scene in 2009, eventually becoming the country’s most powerful political force.

M5S, however, seized power by breaking its rule to never form a coalition. Its tie-up with the League sullied its image among some voters and marked the beginning of discontent within the party, while the subsequent alliance with PD is seen as a betrayal of its origins.

More than 20 M5S MPs have either left the party or been kicked out since it entered government. Gregorio De Falco was the first to be ejected after he voted against Salvini’s draconian anti-immigration bill.

“They lost their ideals,” said De Falco, who is now among other M5S rebels in parliament’s “mixed group”.

A sign that popular measures do not necessarily retain voter loyalty can be gleaned from the basic income. Take-up of the allowance, which Di Maio said would lift millions of people out of poverty, has been the biggest in Calabria, where M5S has lost supporters to the League and its allies. Meanwhile, part of the initiative that was intended to help claimants find jobs has not been implemented.

“The battle over a single law didn’t paid off,” said De Falco.

The PD-M5S coalition’s survival is now hinged on M5S – its largest party – stabilising itself. Vito Crimi, an M5S senator, is at the helm until a new leader is elected in March.

Salvatore Capasso, a former M5S voter who receives about €500 a month from the basic income, said he was sceptical that the protest would be successful.

“I voted for them as they seemed like people who could change the country,” he said. “The income helps but they didn’t keep the promise of helping people find stable jobs. It was a mistake to join with Salvini, and even more so, with PD.”