Immigration New Zealand and its parent - the Ministry of Business, Innovation and Employment - use false social media profiles for investigations and risk assessment, the ministry has confirmed.
The ministry said some staff used false social media personae for intelligence and investigation purposes, such as immigration risk assessments.
Generally, MBIE staff were not authorised to use pseudonyms or false names in their work, a spokesperson told RNZ.
"However, some ministry staff use false social media personas on social media to support verification, intelligence, and investigation work relating to the exercise of regulatory, compliance, and enforcement functions.
"For example, when the Immigration Risk Assessment Team assess reputational and national security risks."
The MBIE revelations came after it emerged last week that some Ministry of Social Development staff used false names on legal documents because, they say, they fear attacks.
ACC staff were also sometimes using pseudonyms in cases where people demonstrated "inappropriate behaviour".
RNZ asked Immigration to explain which migrants, refugees or asylum seekers were the targets of the fake profiles.
The MBIE spokesperson said the ministry took safety and security seriously and sometimes the names of staff and decisions ended up in the public domain.
"This can be difficult for the staff member concerned and the ministry provides support for employees who find themselves in this situation."
Checks can include security vetting by the Security Intelligence Service, biometric checks, and a reputational risk assessment by a unit within Immigration New Zealand.
An MBIE spokesperson said the fake profiles were also used by other enforcement and compliance teams within MBIE, such as teams investigating the sale of unlawful products in New Zealand.
"In the immigration context, other examples of where they may be used are in investigating potential migrant exploitation or the verification of information in relation to visa applications."
Meanwhile, the Ministry of Primary Industries said the department did not generally use pseudonyms to protect staff identities. However, some staff used an identification number rather than their name.
MPI director of human resources Erina Clayton said quarantine officers for biosecurity, and compliance officers such as fisheries inspectors or animal welfare officers, were authorised to issue infringement notices using an identification number.
"This is in order to protect our staff from potentially hostile and aggressive behaviour.
"Our employees are dedicated and professional in the service of New Zealand. We take any threat against the safety of our people very seriously and will take the necessary steps to support them."
Ministry of Justice general manager of health, safety and security Melissa Gill said the ministry had policies to support staff if they were, for example, threatened in court, over the phone or in writing.
"The ministry does not use pseudonyms as part of these responses," she said.
A Ministry of Foreign Affairs and Trade spokesperson said staff did not use pseudonyms, and a Corrections spokeswoman said the department did not have a policy to use pseudonyms.
A State Services Commission spokesperson said the department did not keep records of the use of pseudonyms by agencies.