Bernard Dugué

LONDON — Jérôme Kerviel’s 4.8 billion euro trading loss ($7.1 billion) had a positive effect for Société Générale, at least temporarily.

“The news at Soc Gen may have masked their subprime losses,” said Richard Batty, a fund manager at Standard Life Investments in Edinburgh, using financial-world shorthand for the bank.

The same day Société Générale said that Mr. Kerviel, a rogue trader, had cost it billions, it announced one of the largest subprime-related write-downs by a European bank. Société Générale, based in Paris, said it would write off 1.1 billion euros (now $1.62 billion) related to the United States housing market and 550 million euros ($813 million) related to American bond insurance companies. Only UBS has announced a larger write-down.

Mr. Kerviel’s lawyers, Elisabeth Meyer and Christian Charrière-Bournazel, told Agence France-Presse that Société Générale aimed to “raise a smoke screen that would distract the public’s attention from far more substantial losses that it had made in recent months, notably in the unbelievable subprime affair.”

Though the bank declined to comment when contacted, its chairman and co-chief executive, Daniel Bouton, called the accusations “laughable” in an interview with Europe1 radio on Monday.

Nonetheless Société Générale’s subprime-related losses surprised some analysts, including Jean-Paul Pierret, a strategist at Dexia Securities in Paris. “The bank was perceived as being less ready than others in Europe to take part in the securitization” of debt, he said.

Société Générale’s management indicated its displeasure with the losses. In addition to personnel changes in its derivatives business, it replaced the co-heads of fixed income, Marc Breillout and Grégoire Varenne.

As with UBS, which surprised the markets in December with a record subprime-related write-down among European banks, investors at Société Générale were left in the dark about the possibility of future write-downs. (In November, the bank announced 375 million euros of subprime-related write-downs, insisting that these were based on a “worst-case forward-looking scenario” of total industry losses from subprime mortgages reaching $200 billion.)

It remains unclear how much more European banks will have to write down, and investors are readying themselves for further losses as more banks report fourth-quarter and annual earnings in the coming weeks and months.

Banks worldwide have suffered more than $135 billion in credit losses and write-downs, and some analysts estimate that the write-downs could total as much as $800 billion.

Alain Tchibozo, of ING Financial Markets in Paris, said Société Générale’s subprime write-downs had been in line with his expectations and “not a lot” for a bank of its size. But he said they were greater than he expects from the rival BNP Paribas.

In September BNP, a larger bank, called its risks from United States subprime mortgages “negligible.”

Last month, UBS announced that it would write down $10 billion. Ten days later, another large French bank, Crédit Agricole, said it would take an additional 2.5 billion euros in write-downs after having reported 850 million euros of losses linked to risky American mortgages for the first nine months of 2007.