ROME (Reuters) - A senior figure in Italy’s ruling 5-Star Movement was arrested on Wednesday on suspicion of corruption, dealing an embarrassing blow to group that has always tried to project a squeaky clean image.

Marcello De Vito, the president of Rome’s city council and de facto deputy mayor, is under investigation for allegedly taking bribes from local businessmen in return for favors, legal sources and court documents showed.

Neither De Vito nor his lawyer were immediately available for comment. However, 5-Star leaders who have access to the legal documents responded furiously and ordered his expulsion from the party.

“Marcello De Vito is out of the 5-Star Movement,” party leader Luigi Di Maio wrote on Facebook. “What has emerged in these past hours is not just serious, it is also shameful, morally woeful and is insulting to all of us.”

The scandal comes at a difficult time for 5-Star, which has seen support fall steadily since it emerged as Italy’s largest party in national elections last March and forged a coalition government with the hard-right League.

An opinion poll this week said 5-Star was on just 21 percent, down 11 percentage points from its 2018 election score and well behind the League, which has jumped to 34 percent.

A legal source said De Vito was suspected of accepting bribes in return for helping advance business projects, including the planned construction of a new soccer stadium for Serie A squad AS Roma.

Last year, six people were detained and three others placed under house arrested in an initial investigation of alleged bribery and influence peddling over the long-delayed stadium project.

De Vito’s arrest warrant said he had used his public role to promote private interests, obtaining “sizeable earnings” as a result. “(He) violated the principles of impartiality and fairness to which the administrative action must conform,” judge Maria Paola Tomaselli wrote.

De Vito’s arrest represents a blow to 5-Star’s credibility in Rome. The party took charge of city hall in 2016 after its candidate, Virginia Raggi, was elected mayor, promising to usher in a new, graft-free era after previous administrations were mired in corruption scandals.

Critics say 5-Star has made little if any progress since taking office in resolving Rome’s myriad problems, including a decrepit transport network, pot-holed roads and inefficient garbage service.

Raggi herself was put on trial last year, accused of lying about her involvement in the nomination of the director of the city’s tourism department. She was subsequently acquitted.

“There is no room for corruption in Rome,” Raggi said in a statement on Wednesday. “Those who make mistakes will receive no favors from this administration.”