When Ian Clayton, a retired health and safety professional from Chester, popped into Home Bargains one February lunchtime, he was suddenly approached by a stern-looking member of staff.

“Excuse me, can you please put everything down and leave the shop now?” she said. Clayton recalled how he was stunned, and it was only as he was briskly walked past the tills towards the exit that he stopped to ask what he had done.

“You’ve come up on our system called Facewatch as a shoplifter,” came the reply. “There’s a poster in the window.” With that, he was left outside the shop alone, with a QR code to scan and no idea what had happened.

He is one of a number of people who have spoken to the Guardian after being falsely identified as a thief by shops using Facewatch, a live facial recognition system being rolled out across the UK to clamp down on retail crime.

The company’s website claims that its system has a 99.98% accuracy rate and that last month it sent 50,288 alerts of “known offenders” to shops including B&M, Home Bargains, Sports Direct, Farm Foods and Spar, which all now use the software.

But those who have been wrongly identified and forced to leave shops, either via the technology itself or human error, say they were given no support, and did not know how to complain about their treatment or prove their innocence.

Clayton, 67, said that after he was ejected from Home Bargains he tried calling a phone number on a Facewatch poster, and was sent through to a message saying the company did not take calls and he had to send an email instead.

He was only able to get answers after submitting a subject access request – a formal request under data protection laws for personal information – that revealed he had been incorrectly associated with a shoplifting incident on a previous visit to the shop.

“It was like I was guilty until proven innocent. It’s an awful feeling. It leaves a pit in your stomach and when I look back now I can feel it again,” he said.

“It feels very Orwellian. We’re constantly being recorded and put on these systems but should we be there? It feels like spying without cause. I’m hyper aware of cameras everywhere now, I’m so aware of them.”

Home Bargains eventually issued him an apology and a £100 voucher as a “gesture of goodwill without admission”, on the condition that the details of the incident remain confidential. Clayton declined: “I just thought: ‘Really, you’re trying to buy my silence?’”

As facial recognition spreads across police forces and retail stores, UK biometrics commissioners are warning that national oversight is lagging far behind the technology’s rapid expansion.

Last year, the Home Office admitted facial recognition cameras were more likely to incorrectly identify black and Asian people than their white counterparts, and women more than men, and there have been conflicting studies on their overall accuracy.

Warren Rajah, a data strategist in south London, was asked to put down his shopping basket and leave his local Sainsbury’s store after being told he had come up on the Facewatch system in February.

“For me, this is a civil rights issue that we are slow-waltzing into because if you are just removed without question, your civil rights are being impacted,” he said.

“We already live in a country that has issues with racism, it’s an unavoidable issue. And we know cameras cannot pick up features of people that have darker features with as much accuracy. And this could be happening to people who are much more vulnerable than me.”

He said he had major concerns about this technology being rolled out in police forces, as well as in the retail sector.

“Who is regulating these companies and can they be trusted with our information? And more importantly, no one has actually defined what your recourse is when something goes wrong,” he said.

After countless emails, he eventually found out he was not on the Facewatch database system and staff members had misidentified him. He was offered a £75 voucher as an apology – when he said he did not feel comfortable returning to the store, he was told to use it online.

Jennie Sanders, 48, from Birmingham, was browsing in B&M on a Saturday afternoon last year when a security guard told her she had been flagged up on the Facewatch system and he had to escort her around the store to check she was not stealing.

“I was really upset. It was in front of loads of people, and I was really embarrassed. I said I wanted to leave and he escorted me out of the shop,” she said.

“It was scary but what was more scary was when I got home and started looking into Facewatch, I saw they share the information between loads of retailers.

“I thought: ‘I’m going to be treated like a shoplifter in every store. I’m not going to be able to do any shopping in person ever again.’”

She was told she had to send a copy of her passport to Facewatch to prove her identity before she could find out that she was on the system for stealing a bottle of wine from B&M, which she said never happened.

B&M told her it no longer had any evidence, including CCTV footage from the day, so she was taken off the system and offered a £25 voucher.

“I took a couple of days off work, I was absolutely beside myself. Why was I on a database of criminals without my knowledge?” she said. “I’m never going into B&M again. I try to stay away from places with cameras at all – it has really affected me.”

Sanders said she complained to the Information Commissioner’s Office (ICO), the formal watchdog monitoring how personal information is being used in facial recognition technology, but seven months later she had yet to hear back.

She added: “We’re told to raise complaints and send all correspondence to the information commissioner, but they don’t get back to you. What the hell is happening with any sort of response to the victims of this?”

Rajah had also considered complaining to the ICO, but could find no information on how to do so.

“They are so toothless,” he said. “And this issue has been well reported, and they haven’t publicised a formal complaints process. Where’s that information? How can you complain when there are no avenues to follow?”

A Sainsbury’s spokesperson said: “We have sincerely apologised to Mr Rajah for his experience in our Elephant and Castle store. This was not an issue with the facial recognition technology in use but a case of the wrong person being approached in store.

“The Facewatch system has a 99.98% accuracy rate and all matches are reviewed by trained managers, with additional training provided after this incident to ensure our safeguards are consistently followed.”

Nick Fisher, the chief executive of Facewatch, said: “We are aware of the matters referenced and in each case, we acted promptly once they contacted the Facewatch data protection team.

“These cases relate to human error in the way processes were carried out in-store, rather than any failure of Facewatch’s technology. We are sorry these individuals experienced being challenged while shopping and understand why this would have been upsetting.

“These three errors are extremely rare cases when viewed in the context of the more than 500,000 alerts we send to retailers each year, but we recognise that any mistake is upsetting for the individual concerned. The system is designed to support, not replace, human decision-making.”

A spokesperson for the ICO said: “We recognise the harm and upset that can be caused by misidentification. For this reason, use of facial recognition technology must strictly comply with data protection law and be handled with care and transparency.

“If someone has concerns about how their data has been collected, used, or shared, and those concerns cannot be resolved with the retailer directly, they have the right to raise a complaint with us.

“We also continue to actively regulate in this area and will be publishing further retail‑focused guidance to support retailers in understanding and meeting their data protection obligations, while ensuring the public is properly protected.”

Home Bargains and B&M declined to comment.