The former MI6 officer accused of trying to sell spying secrets is also now charged with trying to trade lists of British intelligence personnel, a court heard.

The new charge against 25-year-old Daniel Houghton was added at a hearing at Horseferry Road Magistrates' Court on Thursday.

Piers Arnold, for the prosecution, said Houghton had "unlawfully disclosed staff lists as a result of which people working for the intelligence services were put at risk by his actions which damaged operational capability", The Times reports.

The half-Dutch computer science graduate was arrested at a central London hotel on March 1, following a sting operation by MI5, which is responsible for counter-espionage.

He is also accused of accepting a briefcase containing £900,000 in exchange for USB sticks and a laptop hard drive containing MI5 and MI6 intelligence gathering techniques up to Top Secret level, the highest classification. He had allegedly sought £2m.

At an earlier hearing it was revealed that British security services acted on a tip-off from their Dutch counterparts. It is unclear which nation's intelligence service Houghton allegedly believed he was selling to.

Houghton has not yet entered a plea. He was remanded in custody until a further pre-trial hearing is scheduled for April 29.

An Old Bailey trial is scheduled for May 27. ®