Daniel Bouton, president of French bank Societe Generale, told the daily Le Figaro on Wednesday he was resigning to "protect" the company.
Bouton said: "I have handed in my resignation. The board will elect a new president on 6 May. I am choosing to go now to protect the bank. I have become the target of incessant attacks that finally damage the company that I am very attached to."
The banker, who admitted "I certainly made errors," said he would leave with no golden handshake.
Societe Generale denied on Monday a press report that it could face losses of up to ?10-billion because of risky investments at one of its asset management units.
"Societe Generale formally denies the claims published by Liberation today," said a statement by the bank, which last year announced losses of ?4.9-billion in a rogue trading scandal it blames on trader Jerome Kerviel.
The left-wing daily Liberation said Societe Generale's SGAM Alternative Investments unit had invested heavily in complex financial products, which had left the bank with ?10.4-billion in "toxic" assets at the start of 2008.
The detailed report, splashed over Liberation's front and four inside pages and headlined "The Other Scandal at Societe Generale," described the products as "unsellable."
It added that "even if... the bank has recorded losses of 'only' ?1.2-billion euros, the final bill could reach 10 billion."
But Societe Generale said that Liberation had confused losses with asset transfers at the division.
It noted that "SGAM's losses for 2008 were ?258-million after tax" as shown in the bank's results statement in February, when it reported a net profit for the year despite the financial crisis.
Societe Generale said net profit for 2008 came to ?2-billion compared with ?947-million in 2007 when it absorbed the huge loss it attributed to unauthorised actions by Kerviel.
The bank shocked the financial world in January last year when it announced the losses incurred as it was forced to unwind more than ?50-billion of unauthorised deals the 31-year-old trader is said to have made.
Kerviel turned himself in to police after the bank revealed the losses and was charged with breach of trust, fabricating documents and illegally accessing computers.