Stenfors was employed as a senior trader on the short term interest rate trading desk of the London branch of MLIB.
The FSA says he deliberately mis-marked the positions he traded on behalf of MLIB between mid-January 2009 and mid-February 2009 by more than £66m ($100m) in order to avoid showing increasing losses in his books.
These actions caused MLIB to make a negative adjustment of more than £300m ($456m) to its books and records.
MLIB was fined almost £2.5m (€2.75m) in October 2009 by the Irish Financial Regulator for failures in respect of circumstances that included Stenfors’ mis-marking.
The FSA says as Stenfors co-operated fully, expressed remorse for his actions and agreed to settle at an early stage, the regulator will revoke the prohibition order after five years in the absence of any new evidence that he is not fit and proper.
FSA director of enforcement and financial crime Margaret Cole says: “Stenfors’ actions in deliberately mismarking his positions fell far short of the FSA’s expectations. Market confidence is likely to be damaged by sudden and unexpected write downs and revaluations of securities. Financial instruments must be priced correctly by traders, particularly in more challenging conditions and when it comes to illiquid products.
“We have banned Stenfors because his misconduct was deliberate, frequent and repeated over a one month period. He was a senior and experienced trader who held a position of trust at the firm. He betrayed the trust placed in him by the firm and demonstrated that he is not fit and proper to be approved by the FSA.”