A rise in the numbers of British food supply workers being forced to self-isolate is being blamed for empty supermarket shelves, as shoppers become alarmed to find shelves and fridges empty.

A surge in workers being alerted by the National Health Service (NHS) Covid app on their phones has hit industries hard because workers have to stay at home.

The app 'pings' users if they have recently come into contact with someone who has tested positive for the virus, asking them to self-isolate. But the app has been criticized for being too sensitive, with more than 600,000 people "pinged" last week alone.

With shops in some areas suffering shortages, and firms in sectors from petrol stations to the postal service affected by absences, the government is being urged to include supermarket staff, lorry drivers and other frontline workers on a list of those exempted from self-isolation rules.

The government has announced that certain industries will be able to apply for staff exemptions, allowing critical workers who are “pinged” by the NHS test-and-trace app to return to work after a PCR test and undertake daily lateral flow tests, rather than self-isolating for 10 days.

But it has yet to publish a list of which sectors can take part in the scheme and there will not be a list of critical workers exempt from automatic self-isolation; instead, exemptions will be considered on a case-by-case basis.

With the number of those expected to be granted exemptions relatively small, bosses are concerned and frustrated that thousands of workers will continue to have to self-isolate when pinged.

Andrew Opie, director of food at the British Retail Consortium trade body, said staff shortages could have an impact on opening hours and shelf stacking.

“The ongoing ‘pingdemic’ is putting increasing pressure on retailers’ ability to maintain opening hours and keep shelves stocked. Government needs to act fast,” said Opie.

“Retail workers and suppliers, who have played a vital role throughout this pandemic, should be allowed to work provided they are double vaccinated or can show a negative Covid test, to ensure there is no disruption to the public’s ability to get food and other goods.”