Potentially millions of users of the NHS Covid-19 app awoke this morning to a worrying phone notification telling them the alert level in the area they lived had changed.

Only, in most cases, it hadn’t.

Overnight the app was brought into line with the new three-tier alert levels and everyone with version 3.7 of the app would have received a push notification, the Department for Health and Social Care told HuffPost UK. (The DHSC couldn’t say how many of the app’s 16m users have this version.)

But anyone not moving into tier 2 or 3 – that is, those in tier 1, or “medium” risk – would have clicked through to find the alert level exactly as it was when they went to bed.

It came just a day after HuffPost UK revealed the government had been forced to upgrade its NHS Covid app to reassure smartphone users worried by alert messages suggesting they have been exposed to the virus.

The NHS app, launched nearly three weeks ago, has been sending alerts to people with the tag line “Possible Covid-19 Exposure”.

But in many cases, the notification simply disappeared once clicked, and was not followed by any official confirmation of contact with a patient.

Now the DHSC has admitted the so-called “ghost notifications” are a glitch caused by Apple and Google’s own bluetooth technology on their phones and are a default privacy setting that it cannot change.

Instead, additional notifications now tell users that there is no need to worry about the “possible exposure” once it has been assessed by the app. Unless, of course, they are one of the unlucky people actually told to self-isolate.

The rollout of the app was hit with a number of other glitches, not least the original government version being the abandoned in favour of a design by tech giants Apple and Google in June.

It was then revealed anyone with some older models of mobile phone would not be able to use the app – and, when it was first released publicly, it did not have an option for users to log a positive test result.