Italy's government risked collapse Thursday as the Five Star Movement, part of Prime Minister Mario Draghi's shaky ruling coalition, planned to abstain on a confidence vote.

Five Star is a formerly anti-establishment party that has plummeted in the polls and lost parliamentarians since joining the government, hurt by policy U-turns and internal divisions.

The decision to walk out during the confidence motion could push the already fractured coalition to collapse and even force early national elections later in the year. 

Five Star head Giuseppe Conte, a former premier, announced Wednesday evening his party's senators would walk out during the confidence vote for an aid package worth about 23 billion euros.

The package also includes a provision to allow a garbage incinerator to be built in Rome -- something the Five Star has long opposed.

Analysts suggested the beleaguered party was not trying to collapse the government but attempting to win back some of its lost support by doubling down on its principles ahead of the scheduled 2023 general election.

Draghi has stated on multiple occasions there will be no government without the Five Star party as members. 

The confidence motion is expected later Thursday following debate in the Senate. 

"If the (Five Star senators) walk out of the chamber today, even if the government has the necessary votes, a new political phase opens," Lorenzo Codogno, a professor at the London School of Economics, told AFP. 

"Draghi would have no choice but to resign."

Nervous investors widened the spread between Italian and German bonds to 221 basis points on Milan's stock exchange on Thursday morning. 

Five Star tensions 

Draghi was appointed prime minister in February 2021 by President Sergio Mattarella and charged with carrying out key reforms required under the EU's largest tranche of post-pandemic recovery funds -- a package worth approximately 200 billion euros for Italy.

The government has since found itself embroiled in the war in Ukraine, taking a strong, pro-EU line, while battling soaring inflation at home. 

Draghi's support of Ukraine, which includes sending weapons and backing EU sanctions, won a parliamentary confidence vote in June despite criticism from Conte that the policy risked fuelling an arms race. 

Since winning legislative elections in 2018 with an unprecedented third of the vote, the Five Star Movement has been losing support and risks being wiped out in national elections scheduled for next year. 

Last month the party -- which had represented the largest in parliament -- split, with Foreign Minister Luigi Di Maio starting a breakaway group. 

Conte, whose party is now polling at 11 percent of the vote, is trying to bring more visibility to Five Star ahead of elections. 

Codogno said he did not believe that Conte was seeking to bring down the government. 

But, he noted, his party "wants to make headlines and make gains in the polls again by running opposition as if it were not in government".

The far-right has seized on the tensions, with the leader of the Lega party within the governing coalition, Matteo Salvini, saying Wednesday that if Five Stars were to sit out the vote, new elections should be called.

"If the decree passes the confidence vote and the Five Stars leave the chamber... I think there is nothing left for Draghi but to go to Mattarella and resign," Franco Pavoncello, a professor of political science at Rome's John Cabot University, told AFP.