A government agency says its internal oversight of a private surveillance firm it uses is adequate.
Immigration New Zealand uses Israeli-US firm Cobwebs Technologies to scan people's social media.
The watchdog of the official spy agencies SIS (New Zealand Security Intelligence Service) and GCSB (Government Communications Security Bureau) does not have any oversight of this.
Immigration NZ said its own internal capability and framework were sufficient.
Asked by RNZ if it was doubling up on what the SIS did, Immigration said it used Cobwebs to meet "legislated responsibility that does not sit with any other government agency".
"MBIE [Ministry of Business, Innovation and Employment] is unable to comment on the activities of the SIS and disagrees with your description of the use of the tools as 'hiring private spies'," general manager of data, insights and intelligence Jacqui Ellis said.
Revealing more about the tool risked compromising its effectiveness against significant threats, it said.
MBIE had "strongly considered the balance between public interest, and privacy and security requirements", Ellis said.
Asked once more about what it was costing taxpayers, she said the ministry's spending was "prudent and efficient".
The government has defended the use of the private surveillance, saying it is vital to detect any risks from thousands of travellers to New Zealand each year.