Navinder Singh Sarao allegedly used a technique called spoofing to manipulate a key U.S. futures market. Above, the home where Nav Sarao Futures is registered, in the Hounslow section of London. Reuters/Neil Hall

(Reuters) - The British trader fighting extradition to the United States on charges that he illegally contributed to the 2010 Wall Street "flash crash", appeared in court on Wednesday and was ordered to be kept in custody after failing to meet his bail conditions.

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.

At a hearing last week, he was granted bail provided he produced just over 5 million pounds and met other conditions.

"Those conditions have not been met and the defendant invites no further order from the court in that regard," his lawyer Joel Smith told Westminster Magistrates' Court.

District judge Jeremy Coleman said: "You have not met the conditions of bail as yet so I rebail you on exactly the same conditions as before. If you meet those conditions, you will be released, if you do not then you will be back here on May 6."

The date for a full extradition hearing was put back from August to Sept. 24 and 25.

Sarao, wearing a grey sweatshirt and tracksuit trousers, spoke only to confirm his date of birth and address. The small courtroom was packed with more than two dozen journalists.

His lawyers declined to make any comment as they left the courtroom.