Prime Minister John Key has signalled the Government Communications Security Bureau faces significant change as it continues to draw criticism over its illegal surveillance of internet entrepreneur Kim Dotcom.
The surveillance by the Government's electronic spy agency was part of a police operation that followed requests by US authorities who want to extradite Mr Dotcom to face charges of internet fraud.
The Labour Party has obtained documents presented to the High Court as part of the legal battle between Mr Dotcom and the Government, and says the Government Communications Security Bureau (GCSB) knew its monitoring was illegal much earlier than it disclosed.
Mr Key has rejected Labour Party accusations about the bureau's illegal activity but says once a review of the agency is finished there's likely to be substantial change.
Labour's deputy leader Grant Robertson says a key document given to the party by the High Court in Auckland is an affidavit from an official at the bureau.
It makes clear the spy agency knew in February 2012 that its surveillance of Mr Dotcom had been illegal.
But Mr Key gives the affidavit little significance and says there is nothing new in Mr Robertson's accusations.