Mr Grillo said on Wednesday the current site in the southern Tor di Valle area was unsuitable for a range of reasons.

In addition, Rome's heritage super intendency said at the weekend that a horseracing course at the planned construction site could not be demolished because of its historic architectural value.

After meeting with Mr Grillo, M5S MP Carlo Sibilia was certain that plans for the new stadium would go ahead.

"The stadium will be built, it's just a question of finding the best solutions to do it," he said.

Mr Sibilia added that technical meetings were still underway, and that there was no risk of Rome city council having to pay one billion Euros in damages to Roma.

MP Lorenza Bonaccorsi of the centre-left Democratic Party (PD), which leads the national government and heads the opposition to Rome city council, criticised Mr Grillo on Thursday for "not allowing [Virginia] Raggi even the possibility of pretending to herself be the mayor".

“A confused state reigns in the Campidoglio, an indeterminacy that verges on exploiting the mentally unfit, holding the capital to hostage," Ms Bonaccorsi added.

Lower House Deputy Speaker Luigi Di Maio denied that Mr Grillo was dictating the situation, affirming that "the decision will be taken by the councillors, the experts and the mayor".

Mr Grillo said on Wednesday that Ms Raggi's failure so far to approve AS Roma's project to build a new stadium in the capital was due to prudence.

"Raggi is acting in a precautionary way," Grillo said of the much-delayed project during a visit to Rome.

A meeting between Ms Raggi and advocates of the project, including constructor Luca Parnasi and Roma General Manager Mauro Baldissoni, has been postponed until Friday.

Roma are talking to Ms Raggi's administration to see if a slightly revised and downsized version of their original project can go ahead and give the club its long-desired private stadium.

At present, the club shares the publicly owned Olimpico stadium with cross-city rivals Lazio.

During a visit to Rome on Thursday, UEFA President Aleksander Ceferin said that if a new Roma stadium is not built "it will be a disaster not only for Roma but also for Italian soccer".

With ANSA