Health staff used a system designed for prioritising deportations when they were deciding whom to take action against for breaking Covid-19 rules.
The Ministry of Health adapted the National Prioritisation Process (NPP), which started being used by immigration officials three years ago.
Immigration New Zealand (INZ) said it helped design the decision-making process for health officials.
It told its former minister, Kris Faafoi, in a briefing that the prioritisation process could be and had been tailored to be used in decision-making in other "high-risk" areas.
"Following on from a review into INZ's compliance deportation and detention activities, the National Prioritisation Process (NPP) not only improves how we prioritise risk and triage allegations, it enables INZ to be intelligence- and data-led: using data, intelligence, and insights to guide MBIE's [Ministry of Business, Innovation and Employment] work in investigations and compliance allegations for INZ in relation to breaches of the Immigration Act 2009, and immigration-related offences under the Crimes Act 1961.
"The NPP methodology is replicable and adaptable. It was successfully tailored to support the Ministry of Health's Covid-19 response to self-isolation non-compliance with support from INZ staff in the design and ongoing processing of non-compliance allegations. The methodology is now recognised across other agencies as an effective and efficient tool to support regulatory decision-making when operating in a high-risk and fast-paced environment."
In an Official Information Act response, INZ said it had been using the National Prioritisation Process since February 2019 and helped the Ministry of Health during Covid-19 as part of the All of Government response, but declined an Official Information Act (OIA) request to say what the criteria were.
"Factors taken into consideration when triaging and prioritising [immigration] compliance activity include the potential seriousness of a legislative breach or risk to the community posed by the breach; and the risk that the breach poses to the strategic priorities of the immigration system, which is focused on supporting New Zealand's economic growth and strengthening our relationships with other parts of the world," its general manager of verification and compliance Richard Owen said.
"The same methodology was applied to potential breaches of the relevant health legislation and public health orders in place to support the Covid-19 response."
Immigration lawyer Nick Mason told RNZ more information was also needed about how the prioritisation policy in INZ compliance was being operated.
"I'm really concerned as to the origin of this programme or this process, because it seems like it has been adapted from something else. If we don't know the prioritisation criteria, which seems like it's very difficult to find out, we can't even tell if it's fair or not."
The agency has run into controversy for other attempts to set out which migrants in breach of their visa it would target - and to define which of them caused most harm to New Zealand, when it was prioritising its compliance resources.
Former immigration minister Iain Lees-Galloway suspended a controversial pilot programme after RNZ revealed the criteria it was using.
And the stepfather of a murdered schoolgirl, and the victim of a serious assault, were both initially prioritised for deportation despite their reasons for needing to be in the country.
A review outlined the failures, including that officers did not know when to use their discretion and that prioritisation within compliance.
RNZ has sought further clarification of the immigration and health prioritisation criteria.
