Italy's far-right Northern League is threatening to bring down the government over a graft scandal involving one of its senior politicians, coalition partner centrist 5-Star Movement (M5S) said on Friday.
The accusation was swiftly rejected by League leader and deputy Prime Minister Matteo Salvini, but the harsh verbal spat underlined how relations between the two coalition allies have sharply deteriorated in the run-up to next month's EU parliamentary election.
The coalition was thrown into turmoil on Thursday when Armando Siri, an economic adviser to Salvini, was placed under official investigation for allegedly accepting 30,000 euros ($34,000) in bribes to promote the interests of renewable energy companies.
Siri was allegedly offered bribes by a man working on behalf of a wind energy businessman with links to top Sicilian Mafia fugitive Matteo Messina Denaro.
According to prosecutors, Siri was not aware of the Mafia connection.
Siri, who serves as an undersecretary in the transport ministry, has denied the accusations. But as soon as news of the judicial probe leaked, Transport Minister Danilo Toninelli, who is a 5-Star member, stripped him of his government responsibilities until further notice.
The unilateral move angered the League and led to furious recriminations between the two coalition partners, who formed a surprise government alliance last May after an inconclusive national election.
"...Even today the League is threatening to bring down the government ... I'm really stunned," 5-Star leader Luigi Di Maio said on Facebook, accusing his government ally of acting irresponsibly.
"It is clear that [he] should resign from the government [...] It is a moral and political question," Di Maio, who is deputy premier like Salvini, said.
In comments that looked certain to further inflame tensions, Di Maio said his party had seen Siri in the past trying to introduce measures that were "a bit controversial."
"We remember them. When they landed on our desk they seemed strange and we stopped them. ... Without us, who knows what would have happened," Di Maio wrote, without giving any details.
Siri made no immediate comment, but Salvini responded with a brief statement. "The League wants to govern well and for a long time in the interests of Italians. Thoughts of a government crisis can only to be found in Di Maio's head," he said.
The League and M5S have in power since June but their time in office has been marred by constant bickering, which recently increased as both parties went in campaign mode for next month's EU elections.
Prime Minister Giuseppe Conte often acts as a mediator. In Siri's case, he said he was withholding judgment because he first wanted to speak with the junior minister.
The 5-Star has vowed zero tolerance against corruption in Italy and has built much of its support on the back of a squeaky clean image. However, its own image has been hit in recent years as some of its own politicians have faced charges of wrongdoing.
Salvini, who also serves as interior minister, accused his coalition allies of hypocrisy by turning on Siri.
"I say to our 5-Star friends they defended (Rome Mayor Virginia) Raggi when she was under investigation. Please do not apply double standards," Salvini said, referring to the fact that Raggi remained in office last year despite being charged with abusing her powers.
She was later cleared of the accusations.
The investigation into Siri is being led by Rome and Palermo prosecutors and concerns nine other people, judicial sources said. Siri demanded to be heard by the magistrates as soon as possible to clear his name.
Siri is a vocal supporter of sweeping tax cuts which are a core League campaign promise and part of the government's programme.
In 2014, he plea-bargained a brief prison sentence over the fraudulent bankruptcy of a company that he was president of. He never served any time behind bars.