Police want to talk to more Government spies over the illegal surveillance of internet mogul Kim Dotcom.
The police investigation into Operation Debut, the lead-up to the raid on the German millionaire's rural Auckland home, will be dragged out further because police say more Government Communications Security Bureau (GCSB) staff need to be spoken to.
The investigation, named Operation Grey, has already faced delays over legal issues about whether the GCSB could reveal secret information.
In a letter to update complainant Green Party co-leader Russel Norman on the investigation's progress, Detective Superintendent Peter Read said investigators had interviewed "some staff" involved in Operation Debut.
"Further GCSB staff need to be spoken to and the information gathered to date needs to be analysed to assess what additional inquiries will need to be completed," he wrote.
He will provide a further update early next month.
The illegal spying emerged last year, when the agency confessed to spying in Dotcom before the raid on his Coatesville mansion in January 2012. The bureau is only permitted to spy on foreigners and Dotcom and his co-accused had New Zealand residency. Questions remain around how long the spying actually went on for.
The GCSB has admitted it acted illegally and Prime Minister John Key ordered an internal review, the results of which are due soon.
Norman lodged a complaint with police in September last year, saying the Government's spies must be held to account.
In December police revealed disclosure issues related to Dotcom's ongoing legal battle against extradition was hampering the investigation, but this was resolved last month.
The US wants to extradite Dotcom on internet piracy charges. Last week Labour accused the Government of casting around for legal advice that suited it in the case.
Deputy leader Grant Robertson released documentation showing legal advice provided to the GCSB changed five times in a week.
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