Facial recognition could be used to replace swipe cards on public transport, the New South Wales government has suggested, but the opposition and digital rights groups say it would pose a risk to privacy.

The transport minister, Andrew Constance, said on Tuesday he wanted commuters “in the not too distant future” to be able to board trains using only their faces, with no need for Opal cards, barriers or turnstiles.

“I’m about to outline some concepts which may seem pretty crazy and far-fetched,” he told the Sydney Institute on Tuesday. “But look at it this way – who would have thought in 1970 that you’d be able to use a handheld device to have a video conversation with someone on the other side of the world?

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“I want people to not think about their travel. To quite literally turn up and go. Customers have already embraced using their credit cards or electronic device to tap on and off trains.”

Constance said he envisioned something similar to Amazon’s “Just Walk Out” technology, which is being trialled in supermarkets. Under that scheme, shoppers are facially scanned, pick the items they want off shelves, then leave. Cameras track which items they took and their accounts are charged.

“In the transport space we’ll use facial recognition technology to scan customers who’ve ‘opted in’ and linked their Opal account,” Constance said. “No more gate barriers – just a smooth journey … It’s all about making the journey easier and faster for people. I am confident we will also see frictionless transport payments in the not too distant future.”

But Labor’s shadow transport minister, Chris Minns, said the idea had come out of nowhere. “It’s a curious speech from the minister,” he said. “Andrew Constance casually announcing his intention to have facial recognition … without any reference to consultation with the community.

“The opposition would have major concerns about this technology being rolled out into the network. The data collected would be of enormous commercial value to whomever owned it.

“NSW taxpayers should not be used by their own government to make money. This government cannot be trusted with this sort of technology.”

Tim Singleton Norton, the chair of Digital Rights Watch, said it was “worrying to see such flippancy from the NSW government on a potential rollout of facial recognition systems across a public service like transport”.

“These are decisions that should not be taken lightly, and require extensive public consultation to ensure that citizens’ rights are not impacted,” he said. “People have a right to expect a certain level of privacy when navigating public spaces, and must have trust that governments are taking appropriate action to protect that privacy.”

Justin Warren, a board member of Electronic Frontiers Australia, said it was difficult to see how an opt-out system could be opt-out when everyone using the transport system would be scanned.

It was unclear how any such system would be comply with Europe’s strict privacy laws, which would apply to European citizens using public transport in Australia, Warren said.

He said there needed to be a public debate about any plans to roll out the technology. “We need to stop taking the framing from government that this is something that needs to happen, and rewind and ask why?”

Warren said he welcomed consultation with Constance on facial recognition.

“EFA would be only too happy to meet with the minister on a regular basis to provide advice on this kind of proposal before it is made public to help the minister avoid making embarrassing statements about technology,” he said.

On Tuesday Constance also discussed the potential for scanners to read a person’s retinas, breath or even walking style – but not necessarily for use on transport.

In the future-focused speech, he said the possibilities of all future technology “are endless”.

“Imagine having a ‘vehicle’ which allows you to do things rather than drive – all legally,” he said. “You could work on a laptop, do a work conference call, watch TV or even read the kids a bedtime story via FaceTime.

“Digital identity verification will eventually be integrated with biometric recognition. This will read someone’s face, retina, breath, gait or voice to enable next level authorisation and access. Think truly contactless payments – entry to buildings, on to planes, at banks and hotels.”

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The minister also described his plan for a potential subscription system for transport “like Netflix”, where travellers pay a monthly fee and can transition between taxis and public transport.

He said such a scheme was already being planned for London, where frequent users were saving money.

“You sign up for a nominal fee each week or month and all the different pricing for public or private providers is built into it,” he said. “This may sound like a pipe dream – but it’s almost a reality in London … I don’t think it’s unrealistic to see the same kind of service being introduced here in Sydney in the near future.”

According to Constance, there has been a 4.7% increase in public transport passengers in the past 12 months. There were 16m extra bus trips in the 2017-18 financial year, compared with the 12 months before.