Internet piracy-accused multi-millionaire Kim Dotcom is using his experience as the subject of illegal GCSB surveillance to urge MPs not to expand the spy agency's powers.
Dotcom, who holds New Zealand residency, is fighting extradition to the US on charges relating to his file-sharing website Megaupload.
The court case revealed he had been illegally spied on by the GCSB, which can only carry out surveillance on foreigners.
An inquiry found up to 88 New Zealanders may have been illegally spied on, but a subsequent report found it did not break the law which was unclear.
As a result, the Government is moving to change the law so the GCSB can carry out surveillance on New Zealanders on behalf of the Security Intelligence Service, police or other agencies, when they have a warrant.
In a submission to Parliament's Intelligence and Security Committee, Dotcom and his co-accused Bram van der Kolk - who also has New Zealand residency - warn against expanding the GCSB's powers without improved safeguards and oversight.
"This bill seems to give the GCSB, a dysfunctional agency which has failed at every turn in recent times, virtually unlimited power to surveil us all at the whim of the prime minister and then to share that information with anyone (including foreign entities)," they wrote.
"The circumstances that we have endured over the past 18 months represent an extreme present day example of what can happen when Government and intelligence agencies misuse or misunderstand their powers."
Dotcom and van der Kolk say any surveillance on New Zealanders should be carried out by the SIS, to prevent information-sharing with overseas agencies.
They also urge MPs to take more time to consider the bill, which was rushed through its first reading under urgency.
The Law Society's submission is also critical of the bill, saying it proposes "a very substantial expansion" of the GCSB's role, and empowering it to spy on citizens and residents is inconsistent with the Bill of Rights Act.
Prime Minister John Key disagrees, saying the bill doesn't expand the GCSB's powers, but enables other agencies to use its capabilities.