The government is “very concerned” about the numbers of people being pinged by the NHS app, the business secretary has told Sky News.

Speaking to Kay Burley, Kwasi Kwarteng said ministers were “monitoring” the situation and would be setting out a list of exempt critical workers “very soon”.

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“The list of exemptions will be quite narrow because, obviously, you have to draw the line somewhere,” he said.

Downing Street said earlier this week that it would not be “producing a list covering individual sectors”, with employers instead having to apply to government departments to allow workers to effectively circumvent the COVID-19 rules around isolation.

His comments come as retailers warn they are under “increasing pressure” to keep shelves fully stocked amid staff shortages caused by the “pingdemic”.

Industry bosses have warned that supply chains are “starting to fail” due to the number of workers, including lorry drivers and meat-processing staff, getting pinged by the NHS COVID-19 app.

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Some shoppers have posted pictures on social media of empty supermarket shelves in parts of the country.

Being pinged by the app means you should isolate for 10 days – but unlike being contacted by Test and Trace, it is guidance rather than legally mandated.

Latest figures show over 500,000 people were pinged by the app in the week up to 7 July, leading to concerns that millions could be forced out of work as coronavirus cases rise.