Freshfields Bruckhaus Deringer and Mishcon de Reya have lined up to advise as JP Morgan moves to sue the former boss of a trader dubbed the 'London Whale' over losses of $6bn (£3.7bn) incurred by the bank.

Freshfields is advising JP Morgan led by employment co-head Caroline Stroud, with Mishcons employment partner Greg Campbell acting for the trader's former boss Javier Martin-Artajo.

The bank issued a claim in the High Court in London last week against Martin-Artajo, who supervised trader Bruno Iksil – known as the 'London Whale' – at the time Iksil is alleged to have made the trades that led to the multibillion-dollar losses.

JP Morgan has filed the claim but not yet served it upon Martin-Artajo, with no details of the exact accusations against the former boss yet disclosed. The losses emerged this summer.

Campbell said: "Mr Martin-Artajo is confident that when a complete and fair reconstruction of these complex events is completed, he will be cleared of any wrongdoing.

"There was no direct or indirect attempt by him at any time to conceal losses."

The news comes after a number of high-profile cases of rogue trading have emerged in recent times, with former UBS trader Kweku Adoboli currently on trial accused of $2.3bn (£1.5bn) in losses through unauthorised trades for the bank.

Bark & Co is acting for Adoboli with Herbert Smith advising the Swiss bank. Kingsley Napley was originally acting for Adoboli until the end of last year.

Meanwhile, former Societe Generale rogue trader Jerome Kerviel lost an appeal last week to quash the allegations of fraud against him with his sentence of three years in prison and order to pay back €4.9bn (£3.9bn) to the bank upheld. France's Veil Jourde has been acting for SocGen on the case.

Click here for a JP Morgan profile from Legal Week Reports.