The developers of the Covid-19 contact-tracing app for England and Wales have stressed that none of the data it uses will be shared with the police.
It followed news that the contact details of people told to self-isolate by the NHS Test and Trace scheme in England would be shared with the police "on a case-by-case basis".
However, the app operates independently of this system.
It has been downloaded more than 18m times since it launched in September.
The news from NHS Test and Trace on Sunday led to worried app users taking to social media to say they would delete it over privacy concerns.
The Department for Health and Social Care told the BBC that neither the police nor the government received any data from the app.
In a tweet, the official account for the NHS Covid-19 app said "The app cannot be used to track your location, for law enforcement, or to monitor self-isolation and social distancing."
#NHSCOVID19app users are anonymous and the app cannot force them to self-isolate or identify them if they are not self-isolating.— NHS COVID-19 app (@NHSCOVID19app) October 18, 2020
The app cannot be used to track your location, for law enforcement, or to monitor self-isolation and social distancing. 1/2 pic.twitter.com/ROB9wweRLp
Recommendations to self-isolate which come via the app are not legally enforceable - unlike an instruction by phone call from NHS Test and Trace.
The app has been built so that not only is all the data it collects anonymised, but it also only exists on individual handsets.
"By its very design the app's data can't be shared, it's held locally on the phone," commented Prof Alan Woodward, a computer scientist from Surrey University.
"Even if the police did get hold of it, it's all anonymised so it wouldn't mean anything to them."
Who runs the NHS Test and Trace app?
By Alistair Coleman, BBC Anti-disinformation Unit
Since its launch, there's been a stream of disinformation about the NHS Test and Trace app, the most common accusation being that it is run by private company Serco.
There have been calls on social media to boycott the app because some people think their personal data is in the hands of a private company.
The BBC spoke to both the Department of Health and Social Care and Serco, and both tell us that the app was made by a partnership led by the NHS involving Accenture, Alan Turing Institute, Oxford University, VMWare Pivotal Lab and Zuhlke Engineering.
Serco has no connection with either the making or the running of the app.
Additionally, Serco has told the BBC that it does not run the physical NHS Test and Trace scheme. That, too, is run by the NHS, with Serco providing about 50% of the phone operations staff for tier 3 contact tracing.