The trader blamed for a 4.9bn-euro ($7bn; £3.7bn) loss at Societe Generale has reportedly said the bank must have been aware of his risk taking.
Societe Generale's management has begun talks which are set to decide the fate of the bank's head, Daniel Bouton.
Jerome Kerviel told investigators that he was "convinced" the bank's bosses knew of his bets but had turned a blind eye, according to French press reports.
Mr Bouton is under growing pressure to take responsibility for one of the biggest trading scandals in history.
However, lawyers for Societe Generale said this was a "lie".
The bank has blamed junior trader Jerome Kerviel for making trades that led to a 4.9bn-euro ($7bn; £3.7bn) loss at the bank.
The scandal is set to dominate a Societe Generale board meeting to be held later on Wednesday.
But Mr Kerviel has reportedly said top bosses knew of his risk taking and turned a blind eye.
It is thought the board will discuss whether or not Societe Generale's chief executive Daniel Bouton should resign.
The scandal has compounded losses linked to US sub-prime debt at Societe General and scarred the bank's image, leaving it vulnerable to a takeover approach.
Mr Bouton offered his resignation after the shocking losses were discovered last week but the board turned down his offer, asking him to lead the bank through the crisis.
Amid concern that a once highly lauded example of French business could fall into foreign hands, French Prime Minister Francois Fillon said on Tuesday that the government would defend the bank against hostile bids.
But many believe his long-term future in his post is untenable, with even the French President Nicolas Sarkozy putting pressure on the bank's top management to accept responsibility for the illicit actions of Mr Kerviel, a junior trader at the bank.
Pressure on the bank has been exacerbated by a group representing employee shareholders taking legal action Societe Generale over its handling of the trading scandal.
Who knew what?
SOCIETE GENERALE IN FIGURES Founded in 1864467bn euros in assets under management (as of June 2007)22.5 million customers worldwide120,000 employees in 77 countries Societe Generale share price
Mr Kerviel, 31, is being investigated for breach of trust, falsifying documents and breaching computer security - but not the more serious charge of fraud.
Societe Generale says Mr Kerviel had an unauthorised position, or a bet, worth about 50bn euros on the future direction of European shares.
To avoid that potentially catastrophic loss, the bank had to unwind Mr Kerviel's trades, but that still cost it 4.9bn euros.
Societe Generale said Mr Kerviel's experience in administrating trades enabled him to bypass strict risk controls. It said he invented deals that, on paper, balanced out his bets.
But in testimony published in the French daily Le Monde, Mr Kerviel said he "did not believe" the bank's senior management would not have been aware of the risky bets he was taking, which dated back to 2005.
"It's impossible to generate such large profits with small positions, which leads me to say that when I'm in the black, my superiors close their eyes about the methods and volumes committed," he was reported as saying.
