New NHS figures show a record 618,903 people were ‘pinged’ by the NHS Covid-19 app in England and Wales in the week to July 14.
The alert warned people that they had been in close contact with someone who had tested positive for coronavirus.
It comes after Business Secretary Kwasi Kwarten said there will be a “very narrow” list of sectors whose workers will be exempt from isolation rules as the Government struggles to contain the “pingdemic”.
Downing Street this week suggested that there would be no list of sectors whose fully-vaccinated workers could face loosened isolation restrictions to prevent staff shortages.
But in the face of mounting pressure, Mr Kwarteng said an updated list of workers exempt from isolation will be released on Thursday.
He said: “We’re looking at different sectors and we will be publishing today the sectors that will be affected.”
Up to 25% of staff at some businesses in the food and drink industry are self-isolating after being pinged by the NHS Test and Trace app, the head of a key industry body has said.
Ian Wright, chief executive of the Food and Drink Federation, told Sky News: “I think the situation is concerning and it’s up and down the supply chain.
“It’s not consistent across the country – there are some places where shops and factories are working perfectly normally and in other parts manufacturers are under extreme pressure to continue producing because they may have up to 25% of their staff off.
“This is partly as a result of structural labour shortages but increasingly the cause is pinging, and it’s getting worse, there is no question about that.”
Mr Wright said the issue was posing a big problem to abattoirs, distribution and to service staff in the hospitality sector.
“As I say, these are not consistent in every part of the country, in every part of the supply chain, but where it’s happening, it’s bad.”
The NHS Covid-19 app uses Bluetooth technology which will determine whether a phone has been within close proximity to another phone using the app for more than 15 minutes.
The app then alerts users when their phone registers that it has been in close contact with the phone of someone who has tested positive for coronavirus.
If you use the Covid-19 app and you have been told to self-isolate it will provide a countdown of days until it is safe for you to end your period of isolation.
Downing Street has said it is “crucial” that people self-isolate after receiving an alert from the NHS Covid-19 app.
No 10 moved to clear confusion after business minister Paul Scully said it was a decision for individuals and employers whether they should isolate after a “ping” from the app.
Professor John Edmunds, a member of the Scientific Advisory Group for Emergencies (Sage), which advises ministers, said: “Contact tracing and self-isolation play an important role in stopping cases getting out of control and preventing deaths.
“It’s important we maintain these measures as stringently as we can.”