He was also named as a "temoin assiste" -- an intermediary status between that of a witness and someone who has been charged -- in connection with fraud, tax laundering, breach of trust and misuse of corporate assets, with the information confirmed by a source close to the case.
The 34-year-old son of France's top diplomat has run into a raft of legal problems over his passion for gambling, with an investigation into his financial affairs opened in late 2011 following a complaint by French bank Societe Generale.
Investigators have also been looking into his 2012 acquisition of a 300-square-metre (3,200-square-foot) apartment on Boulevard Saint-Germain, a chic neighbourhood in the heart of Paris, for seven million euros (USD 7.6 million at today's exchange rate).
But Thomas Fabius has always insisted the property was legally purchased, partly through his winnings and partly by means of a bank loan.
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He is also wanted in the United States for allegedly writing bounced cheques at a Las Vegas casino, with a Nevada prosecutor issuing a warrant for his arrest at the end of October although it is not enforceable outside of the United States.
In one instance, using a chequebook issued by Italy's Banca Monte dei Paschi di Siena, he had written out three cheques to the luxury casino hotel The Palazzo amounting to a million dollars, the US prosecutor said.
A source close to the case, however, said they were not cheques but "IOUs written on paper which have been authorised for payment."
In mid-December, he was questioned as part of a probe into forgery, fraud and money laundering, police sources told AFP.
Approached by AFP today, Fabius' entourage declined to comment on the case.
His father, Laurent Fabius, was appointed French foreign minister on May 16, 2012.