A former Societe Generale futures trader, Jerome Kerviel, 31, found himself at the centre of a fraud scandal last week, which the bank says cost it 4.9 billion euros ($7 billion) in losses.
In an interview with Europe 1 radio station, Chief Executive Daniel Bouton dismissed media reports that Kerviel had wanted to undermine France's oldest bank in the interests of a Russian bank.
Kerviel, who was taken into custody on Saturday by French police, has admitted he carried out illegal stock market deals, said Jean-Claude Marin, the Paris prosecutor.
He added that "the suspect did not act for his own benefit" and earned nothing from the dealings. Kerviel's defense says he was a victim to the bank's operations.
Bouton said Societe Generale was in the process of buying Rosbank, which belongs to Russian metals billionaires Vladimir Potanin and Mikhail Prokhorov, and had all the money for the deal. The French bank already holds 20% minus one share in Rosbank, one of Russia's top thirty.
Yet, the deal planned for February, came under threat Monday over court procedures involving the division of assets between Prokhorov and Potanin. But Bouton assured journalists that the deal, which would eventually grant it a total of 50% plus one share, would be struck on February 11.
The press has been speculating that Societe Generale might soon fall victim to a hostile takeover but Bouton said he had received no proposals of the kind. The French government has promised to defend the bank from a possible merger.
In a statement on Sunday, Societe Generale said it had launched its own investigation into Kerviel's actions. The bank said the trader had broken into the computer systems gambling around 50 billion euros ($74 billion) on future deals. The bank closed the deals but failed to prevent the losses of 4.9 billion euros.
However, French economists have expressed doubts over the bank's statement and said that Europe's top banking group is making a scapegoat out of the trader to cover up its heavy losses caused by the current global turmoil.
French investigators have searched Kerviel's apartment near Paris, and visited the bank's main office. On Monday afternoon, Kerviel is to be released from custody if no charges are brought against him.
The losses are unprecedented in global banking history. Police are also investigating whether more bank employees were involved in the fraud.
Experts expect Societe Generale's net profit in 2007 to reach 600-800 million euros ($884 million -1 billion) despite the losses.
