Trader Jerome Kerviel appeals against conviction

Jerome Kerviel was sentenced in 2010 for losing 4.9 billion euros for his employer Societe Generale (Getty Images)

The appeal of former trader Jerome Kerviel, sentenced in 2010 for losing 4.9 billion euros (about £4 billion) for his employer Societe Generale, has opened in Paris.

Dressed in a blue suit and white shirt, Kerviel appeared calm as the session opened today.

Kerviel was convicted on charges of forgery, breach of trust and unauthorised computer use for covering up bets worth nearly 50 billion euros (about £40 billion) between late 2007 and early 2008. He claims that the bank - France's second largest - was aware of his trades.

Societe Generale has said Kerviel acted on his own and that it cost 4.9 billion euros to unwind the trades.

Kerviel was ordered to pay that sum back to the bank as part of his sentence.

He was also sentenced to three years in prison but was set free pending the appeal.

The 35-year-old former trader looked calm as he entered the courtroom today.

He plans to argue that the bank manipulated some of the evidence used to convict him, saying that a section of an audio recording on which he stated the bank was in the loop had been tampered with.

In April he filed a lawsuit against the bank for obtaining a verdict under false pretences. He also disputes the amount that Societe Generale lost, saying it has recouped some of the money.

"We will explain that the bank knew and when they knew," Kerviel's lawyer, David Koubbi, said recently. "Mr Kerviel has the sad distinction of the most harshly sentenced man in the world."

The bank has denied tampering with the recordings.