WPP is investigating Babila, a rival Italian media company, and de Nardis has been brought in to the investigation for alleged business dealings with the company.
De Nardis, who joins Aegis later in the year, said: "I have no knowledge of being under any sort of investigation and I have no relationship with Babila." However, the Babila chairman, Marco Masieri, is a former brother-in-law of de Nardis.
Benatti, who worked with de Nardis while at WPP, is also reported to be under investigation regarding possible links to Babila.
Babila issued a statement denying any relationship. It read: "Mainardo de Nardis has never had any direct or indirect commercial relationship or any direct or indirect interest in Babila. Marco Benatti has never had any direct or indirect commercial relationship with Babila."
Investigations led by the corporate investigator Kroll and the auditor Deloitte & Touche into WPP's Italian interests were instigated after Benatti's dismissal in January. Last week, the investigations were widened to include Babila and the Italian television production company BRW.
Benatti was fired for failing to declare an alleged financial interest in Mediaclub, a company that WPP acquired in 2003 and for which WPP paid Benatti a £140,000 finder's fee. Benatti asserted he was unaware of his financial interest.
Benatti has subsequently taken legal action against WPP and has threatened to sue the holding company's chief executive, Sir Martin Sorrell, over "the immense damage he [Sorrell] has personally created by his repeated defamatory statements".
Benatti declined to comment on the story.
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