M5S party leader Grillo asserts control over Mayor Raggi.

Rome mayor Virginia Raggi has had her powers reduced by the leader of her anti-establishment Movimento 5 Stelle (M5S) party Beppe Grillo, after the recent arrest of her close aide, the city personnel chief Raffaele Marra, on suspicion of corruption.

Raggi will continue as mayor but Grillo has restricted her power to make “important decisions, such as nominations” without the endorsement of M5S leadership. Grillo also forced Raggi to sack her deputy mayor, Daniele Frongia, and her top political adviser, Salvatore Romeo.

Following Grillo's overhaul of Raggi's inner circle, the embattled mayor told reporters that she would evaluate her position if she were placed under investigation. Grillo wrote on his blog that Raggi had made mistakes and that she “trusted the least trustworthy people in the world”, an apparent reference to Marra, who was arrested on 16 December.

Marra is suspected of accepting an illegal payment from real estate developer Sergio Scarpellini in 2013 while he was Rome’s head of housing policy under the administration of former mayor Gianni Alemanno.

Days before Marra's arrest Raggi also lost her environment councillor Paola Muraro who stood down pending the outcome of an investigation for alleged environmental crimes. Muraro, for 12 years a consultant with the capital’s waste management company AMA Roma, will be heard by prosecutors on 21 December.

Grillo's high-profile intervention in Rome puts further pressure on Raggi who three months ago lost her cabinet chief and budget councillor as well as top managers of transport company ATAC and the head of AMA Roma.

It was reported on 18 December that Grillo had even considered removing Raggi from the party – which prides itself on being the “clean” alternative to mainstream Italian political parties – before deciding that it would be less damaging for M5S if she stayed on as mayor.

Meanwhile, six months after her election, Raggi's team is still not complete.