Accused 'flash crash' trader: 'I did nothing wrong'

The British trader fighting extradition to the United States on charges of having contributed to the 2010 'flash crash' on Wall Street told a London court on Wednesday he had done nothing wrong and was just good at his job.

Navinder Singh Sarao, 36, who traded from his parents' modest home in west London, has been charged by the U.S. Justice Department with wire fraud, commodities fraud and market manipulation.

A trader reacts to the Flash Crash on May 6, 2010.
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"I've not done anything wrong apart from being good at my job. How is this allowed to go on, man?" Sarao said at Westminster Magistrates' Court.

Read More'Flashcrash' trader will fight US extradition

Two weeks ago, Sarao was granted bail pending a full extradition hearing later this year provided he produced just over 5 million pounds ($7.6 million) and met other conditions.

But he has failed to raise the money and his lawyer asked for the bail surety to be lowered to 50,000 pounds on Wednesday. This was rejected by District Judge Elizabeth Roscoe and Sarao remains in custody.

"I will not vary bail. I will leave it as it is," Roscoe told Sarao and his legal team.