Ex-colleague of 'rogue trader' Jérôme Kerviel says bosses knew about him

Bosses of alleged rogue trader Jérôme Kerviel must have been aware of his over-the-top bets, a former colleague told his trial today.

Benoit Tailleu, who at one time headed the Société Générale trading desk where Kerviel worked but left the bank two years before the scandal, said his superiors "could not totally ignore" his activities. "That is certain. It is obvious," he added.

"It's as if Jerome Kerviel had a mandate to buy 10 tons of strawberries but bought 100 tons of potatoes and the supervisor passes through the hangar every day and says nothing."

Tailleu also said Kerviel could not have been a solitary schemer and that the portfolio he managed did not carry great risks.

On the fourth day of his trial, 33-year-old Kerviel's lawyers were trying to show that the bank tolerated risk-taking, which Société Générale has forcefully denied.

Kerviel took risks with up to 50 billion of the bank's money, costing it 4.9 billion once it unwound his positions in January 2008. It remains the largest alleged fraud by a single trader.

He faces a possible five years in prison as well as a 375,000 fine if convicted of forgery, breach of trust and unauthorised computer use. The bank is asking for nearly 5 billion in damages.

Kerviel has said that he believes he is being used as a scapegoat.

The trial is expected to last three weeks.