Officials have confirmed they only became aware of breaches of rules around using false personas on social media platforms due to RNZ's questions.
The Ministry of Business, Innovation and Employment has used false personas in investigations almost 1500 times since 2021, with their use increasing.
It said it did not audit this, though the practice had hit a big controversy five years ago when MBIE admitted using private operators to train its staff in the surveillance.
Instead, after RNZ's inquiries in August, the ministry went looking at who was using them.
In a statement, general manager of immigration compliance and investigations Steve Watson said: "In the course of answering your OIA request, we carried out an all-of-MBIE collation exercise to confirm what units across MBIE were using false personas, the record keeping practices, and the extent of use over the timeframe of your request."
It came across investigators not using the proper controls.
"Some non-compliance with the procedures in the investigations area become apparent."
This triggered a rapid review of false persona use across Immigration New Zealand, Watson said.
This in turn led to the ministry calling a halt on 2 September to the branch using them, while it got the approvals and record-keeping up to scratch.
It used fake personas in criminal and immigration investigations, and to support regulatory compliance, law enforcement and protective security activities, it said.