THOUSANDS of people in England may have isolated unnecessarily due to a UK Government error in its Covid app.

The mistake meant that they were “pinged” by the coronavirus software for a close-contact within a five-day window, rather than a two-day window, a Whitehall whistleblower told The Guardian.

Official guidance for the NHS app had defined close contact as two days before someone was showing symptoms, with the two-day period also the official NHS test-and-trace definition.

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However, the app in England was pinging people who had been in contact with infected individuals up to five days before becoming ill with Covid – three days more than the official NHS guidance.

This meant that thousands of people were self-isolating when they did not need to.

The issue was raised with then health secretary Matt Hancock shortly before he handed in his resignation amid the scandal over his embrace with aide Gina Coladangelo caught on camera.

Hancock's replacement, Sajid Javid, later said the app was being “updated based on public health advice” to a two-day window – despite there never having been online NHS guidance using a period of five days.

The National: Health Secretary Sajid Javid talks to staff during a visit to the Bournemouth Vaccination Centre, in Bournemouth, on August 4. Picture: PA

The source told The Guardian: “The standard definition of a contact in all the scientific and public stuff from Public Health England and NHS test-and-trace is someone who has been in contact from two days before they have symptoms and if they don’t have symptoms but test positive, you go back two days from the test.

“But the app had five days in it. A submission was made to Hancock from test and trace people around the time of his resignation saying ‘it’s five days but it should be two days: should we change it now?' And it didn’t happen.”

The Department of Health and Social Care did not dispute the claims made by the whistleblower.

A spokesperson said: The NHS Covid-19 app is a key tool in our pandemic response, saving thousands of lives and breaking chains of transmission. The app prevented up to 2000 cases of Covid-19 a day in July.

“App users will only ever be advised to isolate if they have been in close contact with an individual who goes on to test positive for Covid-19. It is important users isolate when asked to do so in order to stop the spread of the virus.

“The recent change to the app logic will result in fewer low-risk contacts being advised to isolate, while advising the same number of high-risk contacts to self-isolate.”

The department is thought to have been using a window of five days because it is the halfway point in a 10-day infectious period.