The government has been warned that people could abuse the new coronavirus app by playing pranks on one another.
Dr Michael Veale, a digital rights lecturer from University College London, said the fact that the app relies on users to self-report accurately is “a worry”.
The smartphone download, known as NHSX, is currently being trialled on the Isle of Wight ahead of a proposed nationwide rollout.
But Dr Veale, who is part of a team working on a rival app, said users may play pranks on one another by falesely reporting symptoms and forcing them to self-isolate.
He told Sky's Sophy Ridge On Sunday programme that a critical lack of testing had compromised the app’s potential effectiveness and meant that the UK is effectively the only country to use self-reporting, rather than verified tests.
"That appears to stem from, not a lack of number of tests potentially, but really something that hasn't been focused on enough - the tests aren't fast enough in the UK compared to other countries,” Dr Veale said.
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"And so the UK seems to claim it's stuck using self-reporting because it can't get a test turned around within a few hours.
"And this is really a worry. In other countries we're working with, they are very clear that self-reporting will not be allowed on their app because it can be misused or used to prank or used to target people deliberately and put them into quarantine without them knowing."
Professor Tim Spector, of King's College London, has also accused the government of “putting politics above science” by not working with him on his version of the app - which takes into account multiple symptoms.
"We should be using a combination of symptoms to diagnose this. It would save lives. We are falling behind other countries."
Dr Veale said there are “real signs” the government would be forced to develop a second app in order to avoid a second peak in coronavirus deaths.
He argued that the UK’s use of self-reporting meant that it is currently an “outlier” in the international community and argued the current iteration of the app “won't work well across borders”.
"The Republic of Ireland have already said they're using a decentralised approach, and that will potentially create problems there if the devolved administration chooses to effectively put in this kind of app," Dr Veale added.
Communities Secretary Robert Jenrick denied the Government was already working on a second coronavirus app, but said ministers would move to a different app if necessary.
"As far as I'm aware we're not developing a second app but we are paying attention to the other apps that exist elsewhere in the world," he told the BBC's Andrew Marr Show.
"And if we need to adapt our app or move to a different model, obviously we will do."