Societe Generale came under mounting pressure on Friday to give a full account of how a rogue trader managed to dupe his supervisors and run up a $7 billion loss.
In a sign that the French government was exasperated by the scandal, Prime Minister Francois Fillon openly criticized the bank for not giving him earlier warning that trouble was brewing.
"I was notified, along with all state authorities, on Wednesday," he told a news conference after a meeting with his Luxembourg counterpart Jean-Claude Juncker. "Perhaps the government could have been informed earlier," he said.
Fillon's remarks add to the woes of Societe Generale's top managers, who have squarely put all blame for the fraud on one junior trader, named by his colleagues as Jerome Kerviel, 31.
Commenting for the first time on the world's biggest rogue trading scandal, President Nicolas Sarkozy called it a "large-scale internal fraud."
Sarkozy said the losses "do not affect the solidity and reliability of the French system."
Bank of France Governor Christian Noyer said Societe Generale's accounts were now clean after it unwound the stock index bets placed by the trader, who has not been seen since.
Noyer dismissed speculation that some of the losses pinned on the employee were due to the ongoing global credit crisis.
But he hinted that other French banks could announce writedowns linked to credit losses when they report earnings.
"We know exactly what the exposures are. The provisions have been announced or will be announced in the coming days, where necessary," Noyer told RTL radio.
SocGen shares rose 1.7 percent to 77.14 euros, after having fallen 4 percent on Thursday.
The shares have lost around 20 percent this year due to long-standing rumors about its exposure to credit losses.
Several analysts cut their recommendations for the bank's shares.
A lawyer claiming to act for Kerviel said that unlike Nick Leeson, who broke British bank Barings with similar unauthorized trading losses in 1995, he had not gone on the run and was available to co-operate with investigators.
SocGen and senior French political and financial figures poured blame for the incident solely on the man whose frowning image from an office directory has been flashed across the world's financial TV bulletins and news websites.
But the bank is also under pressure to explain how a man variously painted as a genius or junior office plodder earning less than 100,000 euros a year, ran rings around the bank's sophisticated anti-fraud systems from a desk at headquarters.
"They are saying all of this was cunningly concealed, but somebody must have been funding the collateral or whatever was needed to sustain those positions," said Derek Chambers at Standard & Poor's Equity Research.
Others questioned how other banks and market players that did business with SocGen could have been in the dark so long.
"There's still a feeling of total incomprehension," said Agilis Gestion fund manager Frederic Hamm. "How come the intermediaries never alerted Societe Generale?"
The head of Italy's second-largest bank, Intesa Sanpaolo, said the scandal had dealt a new blow to the image of the banking industry, already reeling from the subprime crisis.
"It's something that further damages the image of banking at a time when people are already very concerned about risks," chief executive Corrado Passera told Reuters on the sidelines of the World Economic Forum in Davos.
Even France's super-rich gaped at the sums involved.
"It is incredible that one guy can run up loses of such an amount. 4.9 billion. That's serious money," billionaire Vincent Bollore told reporters on a press trip.
"They must be drinking champagne at BNP Paribas now," he added, referring to past attempts by BNP to acquire its cross-town rival.
BNP Paribas analysts estimated that SocGen's trade exposure had been in the order of 33 billion euros. Other estimates ranged from 20 to 50 billion, staggering sums to be tossed around the global electronic marketplace by one person.
A source close to French banks said SocGen had been nursing losses of about 1.2 billion euros when the trader was finally unmasked and summoned to the office to face the sack on Sunday.
The loss spiraled to 4.9 billion euros after SocGen opted to close the positions as soon as already battered markets reopened on Monday -- a fateful decision that coincided with the worst one-day fall in stock markets since Sept 11, 2001.
In full page advertisements in France's leading newspapers, Chairman Daniel Bouton apologized to SocGen shareholders, but analysts questioned whether a stay of execution granted him by the bank's board would last long.
"I understand perfectly your disappointment and see your anger. This situation is completely unacceptable," Bouton wrote.
SocGen had built up a reputation as home to some of the world's most complex finance. The respected Financial Times Lex column coined a new nickname for the bank: "ShockGen."
Analysts said the debacle had intensified long-standing speculation that SocGen would eventually be taken over.
Rival BNP failed in a hostile bid for SocGen in 1999 and has been seen as a dormant predator ever since.
A source close to several French banks, however, expressed doubts that SocGen would become the target of a hostile bid in the immediate future.
"The idea of one in such a situation is hard to conceive; how would you justify going in when you won't know where the skeletons are?" the source said, asking not to be named.