The former wife of Scot Young, who plunged to his death on to railings outside his fourth-floor London flat last week, had challenged him just weeks before about his links to a notorious crime gang.
Michelle Young believed he was associated with the Adams family, who have been linked to drug trafficking, money laundering and murder, a Sunday newspaper has reported.
Reports since Mr Young’s death have suggested he was murdered by the Russian mafia but the Metropolitan Police have stated his death is not being treated as suspicious.
According to the Sunday Times, Mrs Young who was embroiled in a bitter £20 million divorce battle with him felt some of his wealth might be from organised crime and she had asked HM Revenue & Customs (HMRC) officers to investigate his links to the family and other underworld figures.
Mr Young went to prison after failing to disclose details to the divorce court of how much money he had.
The former Dundee businessman the son of ex-Dundee United player Duncan Young was thought to have amassed a vast fortune through property dealings.
He was found dead last Monday afternoon, impaled on railings after falling from his flat in Marylebone.
Mrs Young had written to HMRC claiming her husband was involved in criminality and “tax evasion and fraud”, and she believed he was laundering his own assets to conceal the original source and destination.
One corporate investigator who worked on the case told the newspaper he believed significant proportions of Mr Young’s wealth were funds held on behalf of other business associates.
The paper said the 52-year-old was once thought to be worth around £400 million and a failed property investment deal in Russia had led to his death.
Other reports have claimed Mr Young’s plunge should be investigated more thoroughly by police after it was revealed that five of his close friends have also died in mysterious circumstances over the past few years.
Stewart Lansley, an expert on Russian crime, said the circumstances of all six deaths merit a full investigation.
He said: “The whole world of Russian emigrs and oligarchs has always been surrounded by mystery and intrigue.
“It seems there are so many of these accidents within these circles that it does raise question marks and this is something you do feel needs looking into.”
Meanwhile, international finance expert Burke Files said there is “no way” Mr Young threw himself to his death.
Based in Boston, Mr Files said: “The sort of man who prefers to go to jail instead of telling the court about his finances isn’t the sort of man who chucks himself out of windows.”
While the Metropolitan Police initially said there were no suspicious circumstances surrounding the tycoon’s death, there is now increasing pressure for a deeper investigation.