The NHS is drawing up plans that could see it expand the remit of its coronavirus contact-tracing app to enforce social distancing by warning people if they spend too much time outside.

The smartphones app, currently under development at the health service’s innovation unit NHSX, is expected to be released within weeks. Its main purpose has been reported as “contact-tracing”: it would keep tabs of users’ encounters with their contacts through Bluetooth, and then automatically notify those people if a user is infected with coronavirus.

Internal documents seen by WIRED reveal that the people working on the project are exploring whether the app could be retooled with extra functions that could allow it to boost social distancing measures that have been in place since March 23.

These distancing measures could be accomplished by using the app to notify users if they spend more than one hour out of their houses by nudging them to go back home, or to warn them if they are coming too close to other groups of people who have downloaded the app.

WIRED understands that the decision to assess the potential addition of these features was taken following a meeting between health secretary Matt Hancock, the government’s chief scientific Adviser Patrick Vallance, and NHSX CEO Matthew Gould.

At this stage, the inclusion of such features is still only hypothetical. NHSX is currently in the process of assessing all the possible ways the app might be harnessed to support social distancing; later this week the health secretary will draw upon that assessment to make a decision, and possibly start working out the legal and policy details of how such functionality could be implemented. The final call on a roll-out will have to involve several governmental organisations, most notably the Cabinet Office.

The documents seen by WIRED suggest that, when the lockdown is relaxed, the app might also play a role in a system providing “immunity passports” to people who have contracted and recovered from the novel coronavirus.

An NHSX spokesperson said that "NHSX is not developing any product to be used for enforcement purposes."

Rachel Coldicutt, a technology expert and ethicist who runs the technology consultancy Careful Industries – and the first signatory of an open letter calling on NHSX to follow “ethical best practices” in designing the app – says it unlikely that the plans to use the app to enforce social distancing will ultimately be adopted.

“For that to happen in the UK, we would have to be quite in a very bad position indeed. I can’t imagine a Tory government announcing that,” Coldicutt says. She adds that, since downloading the NHS app will be voluntary, the lurch to a more nagging vibe might hinder adoption.

“When you start layering in things that might be monitoring people’s whereabouts – especially with a voluntary app – the likelihood of people downloading it would be extremely low. People will leave their phoness at home when they plan to stay out for longer than an hour,” she says.

“On the other hand, there would be certain ways of framing [these features], if you want to make it more attractive. For instance, you could add a feature showing if nearby supermarkets are busy or not,” a concern which she says several people have been voicing in the past few weeks.

Silkie Carlo, director of the pro-privacy campaign group Big Brother Watch, criticises the plan, saying that “a government-backed locations tracking app risks the most insidious mission creep.”

“If authorities use this crisis as an opportunity to extend surveillance, they will haemorrhage trust and undermine important public health measures.”

News that the government – through NHSX – was planning the launch of a contact-tracing app first emerged last week, in a report by Sky News. The report revealed that the technical side of the development had been contracted out to US technology firm VMware, while the algorithm had been designed by the University of Oxford’s Nuffield Department of Medicine.

Gian Volpicelli is WIRED's politics editor. He tweets from @Gmvolpi

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This article was originally published by WIRED UK