"We defended Jerome Kerviel vigorously and I confirm that despite all the evidence put forward by the defence, it was not enough to dissuade [the court] against the original verdict," said David Koubbi.

"Our aim was to defend Mr Kerviel against a lamentable injustice. I admit we have failed.

"We will continue to support Mr Kerviel in his fight and we will now decide with him if we can take this further with the court of cassation."

French regulators have also fined Socit Gnrale 4 million euros for failures in its internal risk management systems following the scandal.

The bank spent 130 million between 2008 and 2009 to strengthen its systems and controls. But in August 2010, it was fined £1.6 million by the UK Financial Services Authority for failures that meant it was inaccurately reporting four in every five of its transactions.