Stuff takes to the streets of Wellington to ask members of the public how they feel about the use of facial recognition technology by some supermarkets.

The Privacy Commissioner says police should have consulted him on their new facial recognition system.

Stuff revealed on Thursday police had enlisted the services of American company Dataworks Plus to upgrade their existing biometric system.

The new tech will include what the company described as a "state-of-the-art" facial recognition system, that will be able to search photographic stills from CCTV footage against a database of faces held by police.

AP A man watches as a visitor tries out a facial recognition display at a booth for Chinese tech firm Ping'an Technology at the Global Mobile Internet Conference (GMIC) in Beijing in 2018 (file photo).

New Zealand Police said it did not need to consult the commissioner as the project was an upgrade of an existing system.

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But it is understood the previous system, rolled out a decade ago, is now so outmoded it is rarely used, if ever.

SUPPLIED Privacy Commissioner John Edwards says he should have been consulted on the upgrade of the police biometric system.

Privacy Commissioner John Edwards was in the dark on the progress of the controversial system's procurement process until Stuff revealed it was in its "detailed design stage" after obtaining a trove of documents under the Official Information Act.

"I learned about it from you," he told Stuff.

Edwards had not been consulted on the project or its wide-ranging privacy implications.

STUFF Supermarket giant, Foodstuffs is using facial recognition in some stores.

"I would expect to be consulted on a matter that has such potentially significant privacy concerns, and involves new technology developed in a completely different jurisdiction with a completely different population."

One of the documents showed police want the photo database to be able to import images of prisoners, firearms licence holders, missing persons and registered child sex offenders.

Police also want the system to be able to capture, store and search clothing descriptions, tattoos, scars and other marks.

The use of facial recognition systems by law enforcement has been dogged by controversy, often centred around accuracy.

Facial recognition technology trialled by London's Metropolitan Police mis-identified members of the public as potential criminals in 96 per cent of scans in London, the Independent reported in May.

Asked about the reliability of the system, Dataworks Plus executive vice president and general manager Todd Pastorini earlier said: "We don't make accuracy statements."

GETTY A display for facial recognition and artificial intelligence is seen on monitors at Huawei's Bantian campus on April 26, 2019 in Shenzhen, China (file photo).

Edwards said the accuracy of any such system should be carefully scrutinised before it was implemented.

"When you're talking about technology such as this, which can be quite population specific, it really warrants a close examination of the input data and the accuracy rate."

He believed at a bare minimum police should undertake a privacy impact assessment.

But he also suggested a cost-benefit analysis should be conducted.

"If you're spending 10 million [dollars] on a system that is actually not going to materially improve policing, then you should actually spend that 10 million somewhere else that would."

Asked if they had or would conduct a cost-benefit analysis of the project to upgrade their biometric system, a police spokeswoman said: "A Post Implementation Review is planned that will determine if the project has delivered the anticipated business needs, improvements, and benefits."

Police refused to immediately say the cost of the project.

In an emailed statement, a police spokesman said the police chief privacy officer undertook a privacy analysis of the project.

"Police are confident the systems involved, which already host biometric identity data safely, are robust and well managed.

"Police consult with the privacy commissioner on a range of projects involving technology and business processes, however it is not mandatory for all projects.

"As this project involved an upgrade to an existing system, consultation with the privacy commissioner was not required."