The trader fired by Mitsubishi Corp for allegedly losing $320 million in unauthorized bets on the price of oil denied wrongdoing in a statement issued by a lawyer on Wednesday.

Wang Xingchen, also known as Jack Wang, did not engage in unauthorized trades in crude oil derivatives at Petro-Diamond Singapore (PDS), a division of Mitsubishi, according to Joseph Chen, a Singapore-based lawyer who claimed to be working on Wang's behalf.

"Our client's instructions are that the trades had been reviewed by PDS' financial team and the losses were not caused by him but by Mitsubishi's decisions," Chen said in a statement.