Jerome Kerviel, who stands accused by Societe Generale of losing the bank $7.2 billion due to rogue trading, has claimed that many of his colleagues were also guilty of fraud.
Admitting that he breached legislation, the 31-year-old said he was not the only worker at the bank to flout the law.
Mr Kerviel has been formally charged with fraud, forgery and breach of trust but his lawyers claim he had "committed no dishonest act" and had been made a scapegoat by the bank.
Co-workers including security checkers and managers have been implicated in the futures trader's dealings.
Prosecutor Jean-Claude Marin said: "There were other traders who had acted in a similar way by exceeding their trading limits."
However, Soc Gen chief executive Daniel Bouton said: "This fraud has been committed by a great pretender, who has succeeded in navigating the many sophisticated control systems that we have, to permanently conceal what he was doing, while also going about his normal activities."
Mr Kerviel has admitted that he hacked into computers and faked e-mails to hide his trading positions since 2005.