When “superb talent” Valery Gergiev was first unveiled as the honorary president of the Edinburgh International Festival he was also lauded as a “truly international figure and a great humanitarian”.

The Russian conductor would soon be described as “the most powerful man in classical music”.

Jonathan Mills, then the Festival director, said he gave the job to Mr Gergiev in 2011 “because his artistic values parallel those of the EIF”.

But last month, after the tanks of Vladimir Putin’s army tore over the Ukrainian border, Mr Gergiev, long described as a friend and confidant of the Russian president, was forced to resign.

Now investigators working for jailed Russian opposition leader Alexei Navalny have uncovered a vast undeclared fortune in the name of Mr Gergiev or companies he controls, including a $100 million Italian property portfolio featuring two canal-side palazzi in Venice.

The Navalny Team have also obtained detailed financial documents they say show Mr Gergiev using his state-financed charity as his “personal wallet”.

Read more: President of Edinburgh Festival Valery Gergiev quits amid pressure to denounce ally Putin

In a documentary video published on Youtube the investigators said the conductor used funds from the foundation, which carries his name, to pay for everything from lavish dinners, alcohol and cigars and trips in private jets to the utility bills for one of his many homes.

The conductor is officially director of St Petersburg’s outstanding Mariinsky opera theatre.

That is a government job and he is therefore supposed to make a full declaration of his property. He has not submitted any such document in the last five years, the Navalny Team said.

Mr Navalny and his colleagues made their names producing forensic but evocative videos and articles about the hidden wealth of Russian political elites, including Putin’s alleged Black Sea palace.

Their findings are sometimes countered and Mr Gergiev has yet to respond to their documentary.

He does appear to have legitimately inherited chunks of Italian real estate from a Japanese harpist – a close friend–- who had married an aristocrat.

The Navalny Team, however, has levelled serious accusations. “He may be a the greatest musical genius on earth but unfortunately that does not change the fact that he is a fraudster and a thief; that his talent goes hand in hand with lies and financial machinations involving billions of rubles of public money,” they concluded.

Mr Gergiev was fired from prestigious roles in Edinburgh and Munich – and his concerts cancelled in Milan and New York – after he refused to condemn Putin’s invasion.

Some critics say artists should not have to answer for the crimes of their governments.

HeraldScotland: Russian opposition leader Alexei Navalny (AP Photo/Alexander Zemlianichenko, File).Russian opposition leader Alexei Navalny (AP Photo/Alexander Zemlianichenko, File).

The Navalny Team, however, described Mr Gergiev as a “court musician”, as a “shadow foreign minister” and as Putin’s “ambassador in the cultural world”. For them, the conductor is not just a supporter of the Putin regime, he is the Putin regime. His foundation was bankrolled by state enterprises and banks and Kremlin-linked oligarchs.

The Navalny Team – whose own hero was jailed for nine years for what they see are trumped-up charges of embezzlement – want Mr Gergiev to face western sanctions.

Mr Gergiev’s politics and association with Russia’s autocratic ruler have been well known for some years, including while he served as EIF president.

SNP MP Martin Docherty-Hughes said it should serve as a warning to Scottish cultural organisations when they engage with individuals linked to authoritarian states.

He said: “These revelations are about a lot more than the actions themselves: they speak to a deeper malady, one where the tools of the state have been turned not to serving the majority of Russia’s citizens, but to enriching and empowering the select few: and there were few who were more select than Valery Gergiev, quite possibly Russia’s greatest living cultural icon.

“The way that this ‘great humanitarian’ was until recently lauded by cultural organisations like the EIF also speaks to the malady that affected so many in the West. While his close friendship with Putin was well known, the intangible benefits of ‘cultural exchange’ were placed above any sort of due diligence on the suitability of this man to hold such a distinguished role in our cultural firmament.”

The EIF had no comment. Putin late last month suggested Mr Gergiev should consider taking on Moscow’s Bolshoi as well as the Mariinsky, reprising an old tsarist role as a kind of court maestro. Russian TV has accused British authorities of “cancelling everything to do with Russian culture”.

The Russian Government has declared the Navalny Team to be extremist. Its activities are banned.