Javier Martin-Artajo, a former banker who oversaw synthetic credit trading in JPMorgan Chase (JPM) & Co's London chief investment office, has slapped a lawsuit against UK Financial Conduct Authority last week at a tribunal, Bloomberg noted. The UK court's online website did not provide any details about the case filed by the ex-trader against the financial regulator.

The news agency said Martin-Artajo first surfaced in the media when he was indicted in September last year in the Manhattan federal court for conspiring with Frenchman Bruno Iksil, the "London Whale," to hide losses incurred by the JPMorgan London unit. In a parallel lawsuit, the US Securities and Exchange Commission has also claimed that Martin-Artajo and a subordinate, Julien Grout, were part of a scheme that padded the performance of their portfolio to curry favor with their superiors, Bloomberg added.

Martin-Artajo had asked a Madrid court in November last year to not extradite him in relation to the cases filed against him as he argued that the alleged events had happened in the UK as opposed in the US. Bloomberg said Martin-Artajo is a Spanish citizen.

It was noted that Martin-Artajo was not the only one who had challenged the FCA. In October 2013, international CIO head Achilles Macris at New York-based JPMorgan had filed a separate lawsuit against the financial regulator. Lawyers for Macris had said that their client complained that the FCA did not give him the opportunity to respond to the regulator's findings about the losses. Macris and Martin-Artajo's cases were both not available for public viewing.

Following the cases filed against Macris and Martin-Artajo, the FCA ordered their former employer to pay $228 million or 138 million pounds in September after finding that the London management of the CIO had misled the two traders. According to the regulator's report about the fine imposed on JPMorgan, Macris nor Martin-Artajo were not mentioned nor they were accused of any wrongdoing.