The embarrassing U-turn comes after officials concluded it was technically impossible to create an effective app that did not conform to the Google and Apple model, but that a straight switch to their model would not solve all the problems.
They said there were also significant problems with the Google–Apple approach and they hoped to find a “third way” by working with the two firms to create a tracing app that would work.
The idea behind the app was to track anybody that a person with coronavirus symptoms came into close contact with, using the Bluetooth connectivity on their smartphones.
But the ditched app designed by the government only recognised 4% of Apple phones and 75% of Google Android phones during the weeks of testing on the Isle of Wight.
While the alternative Google-Apple model identified 99% of phones, it could not accurately measure the distance between two phones, making it unclear when somebody would fall in or out of the 2-metre physical distancing range.
Officials would not immediately disclose how much money had been spent on developing the failed app. No launch date for the new app has been announced, but officials are hoping for a contact-tracing app based on the Google-Apple model to be launched in the autumn or winter.
The NHS had hoped to build an app that kept an anonymised central database of anybody an infected person had come into contact with. But Apple and Google refused to endorse that approach and said they would only redesign their operating systems for governments that used a decentralised approach, where no data was held in a single official database.
NHS developers spent weeks trying to find a way of making their approach work, but it failed because once Apple phones had “gone to sleep” because they were inactive, they stopped communicating via Bluetooth.
Matt Hancock, the health secretary, had promised the app would be ready by mid-May and reports in the Guardian that the government was considering switching were vehemently denied.
But on Wednesday the digital minister James Bethell admitted the app would not be ready until winter, a sign of how little practical progress had been made. There have been so many delays that administrations of Scotland, Wales and Northern Ireland had not confirmed they would use the app.
The decision to switch to the Google-Apple model will have wide-ranging ramifications for the government’s contact-tracing programme. The Californian tech companies’ unbending rules greatly limit the amount of data the NHS can access, preventing the health service from using the app to increase its understanding of the spread of coronavirus around the UK.
Jonathan Ashworth, the shadow health secretary, said: “This is unsurprising and yet another example of where the government’s response has been slow and badly managed. It’s meant precious time and money wasted.
“For months tech experts warned ministers about the flaws in their app, which is why we wrote to Matt Hancock encouraging the government to consider digital alternatives back in May.”
Earlier this week Germany launched its own contact tracing app based on the Google-Apple model. On its first day, it was been downloaded 6.5m times.
The new model will force a shift in focus: the current contact-tracing app operates on a two-tier system, where users are notified if they have been in contact with someone with Covid-19 symptoms, and then warned again if that person has a positive test. That choice was made in part because the government wanted to minimise the delay between onset of symptoms and sending out a notification.
Without a centralised gatekeeper to prevent malicious users from falsely claiming they have symptoms, the NHS will be forced to only allow users who have a positive test result to send out exposure notifications – a problem cited by GCHQ as one of the main reasons to use a centralised model in the first place.
The switch will also do little to solve one of the most pressing problems, which has plagued not only the Isle of Wight tests, but other contact-tracing apps around the globe: the fact that the Bluetooth signal the app relies on is an unreliable way of estimating distance.
This problem, which is unrelated to whether the app uses a decentralised or centralised approach to data, means two phones kept in pockets on a crowded train can “think” they are very far away from each other despite being within 2 metres, while two phones in active use outdoors can “think” they are very close, even if they are in fact well out of the danger zone.
Sal Brinton, the Lib Dem health spokesperson in the Lords, said: “Lord Bethell and Dido Harding [who is in charge of the test and trace programme] have already said that it will be some months before England has that full service, probably winter. We need it now, and changing to an app that still has technical issues with Bluetooth distracts from the importance of fast, effective tracing by experts.”