Stéphane Richard, the head of telecoms company Orange and a former aide to IMF chief Christine Lagarde, was charged Wednesday with fraud in a corruption probe dating from her time as France's finance minister.
Reacting to the charges, he was described as being in "confident and combative" mood by close friends.
Richard was Lagarde's chief of staff when, in 2008, she sanctioned a state payout of €400 million euros to disgraced tycoon Bernard Tapie.
Richard had been taken in for questioning on Monday, along with Jean-François Rocchi, who headed a financial institution created to hold the non-performing assets owned by the Credit Lyonnais bank, the source said.
The International Monetary Fund chief was questioned for two days in May about the €400-million payout to Tapie, but she avoided charges and was instead named an "assisted witness".
The arbitration followed a dispute between the businessman and partly state-owned bank Credit Lyonnais over his 1993 sale of sports group Adidas.
The panel upheld Tapie's claim that Credit Lyonnais had defrauded him by intentionally undervaluing Adidas at the time of the sale and that the state, as the bank's principal shareholder, should compensate him.
Orange had said on Monday that Richard would continue to remain the company head.
Investigators have also been probing whether Tapie was favoured in return for having supported ex-president Nicolas Sarkozy, Lagarde's then boss, in the 2007 presidential election.