Pubs and restaurants were asked to carry out contact tracing calls to customers in breach of data protection rules, leaked documents reveal.
Confusion within the Test and Trace system and failures of the £40 million Covid app prompted desperate health officials to co-opt hospitality businesses into warning patrons about outbreaks despite it being unlawful.
An internal report found that lack of guidance from Test and Trace for local public health teams on how to handle the data left businesses "being asked to, or volunteering, to contact customers and visitors".
It added: "This is a breach of General Data Protection Regulation (GDPR), and leaves businesses and venues open to potential legal challenge."
Despite hundreds of millions of people who visited pubs, restaurants and hairdressers before lockdown leaving their names and contact details, the information was barely used by Test and Trace, according to the report, seen by Sky News.
The report admits that potentially "thousands of people" were not warned they might be at risk of infection, "potentially leading to the spread of the virus".
The failure of the QR code alert system was partly to blame. App users were asked to use their smartphones to scan the code – unique to each venue – on the way in, enabling them to be alerted if an infectious person was there at the same time.
When the technology was introduced in October, ministers hailed it as a crucial step to curbing the pandemic and passed laws making it illegal for venues not to display a QR code.
However, according to analysis by software developer Russ Garrett, only 284 alerts were sent for 276 venues. The report admits the app was "not fully" utilised.
Instead, local public health teams were tasked with contacting venues to obtain check-in data, as well as flagging risky venues to the Test and Trace team so that alerts could then be sent out via the app. The report said a new system had since been put in place to allow Test and Trace to "centralise" the contact tracing process.
A spokesman for the Department of Health and Social Care said: "The NHS Covid-19 app is an important tool in our pandemic response. It has instructed hundreds of thousands of people to self-isolate since it launched and it has been hugely effective at breaking chains of transmission, preventing an estimated 600,000 cases."