Officials admit they have been using facial recognition to identify people for years without knowing if it distorts results for Māori.
This is disclosed in memos about the powerful new Identity Check online verification system the government is developing, newly released under the Official Information Act.
A memo in June said Internal Affairs had used biometrics for years for passports and digital citizenship services.
"While these services have been developed with best intentions, unanswered questions remain regarding demographic differences in the underlying biometric technology and whether Māori perspectives and needs have been adequality represented in the service design," department managers said in the internal document.
Facial recognition accuracy is improving but has been less accurate for brown and black people, than white people, for many years.
Identity Check takes its rollout in public much further, potentially expanding facial recognition for online identity-proofing across thousands of agencies and even private companies.
People wanting to readily get a passport have had no choice for years but to use facial recognition.
"While the biometric systems we use are simply comparing data and not making judgements on people or access decisions for individuals ... if there were significant differences in algorithm performance between demographic groups, it is possible this might contribute to distorted outcomes for people," the memo said.
This might force some ethnicities to use "alternative, less convenient, identity-proofing options, reducing trust and confidence in the service and the department".
Internal Affairs has previously repeatedly assured the public in statements to RNZ that public trust was its number one priority, and that it had engaged properly with Māori as the waves of biometrics swept around the globe.
But the OIA memos show the officials did not do this and are now trying to catch up.
"In recent years general concern with the use of biometrics has grown and the department has yet to meet its obligations to seek and consider the views of Māori (in relation to its use of biometrics) as partners under the Treaty of Waitangi," its June memo said.
It noted "some criticism from the media" in 2022 about the use of biometrics in Identity Check and "the lack of any specific consultation with iwi". It had told RNZ at the time it had engaged properly.
But a privacy impact assessment in September 2022 said: "To date no specific Māori engagement has been conducted regarding Identity Check."
The assessment did not mention Te Tiriti at all.
"The department has since made commitments to ministers that we would complete consultation with iwi in relation to the biometric services used by Identity Check and work to address any identified concerns," the June 2023 memo said.
At midyear, it had only "consulted internally".
By last week, when it issued a statement to RNZ, the department had agreed on "an approach for engagement with Māori" and assigned a leader, though not actually done it. A timetable lays out how this might happen over the next three years.
"Testing and research into biometric performance will include guidance by our findings from dialogue with Māori, ie, are there issues with Mataora facial markings," a memo said. Mataora is male facial tattooing.
A second privacy impact assessment on Identity Check is being done to take account of it having to upgrade the failed facial recognition function.