Iceland has been forced to close a number of stores due to a staffing crisis caused by the 'pingdemic'.
The supermarket has revealed a high number of employees are isolating after being contacted by the NHS track and trace app.
It comes days after Freedom Day in England, which saw the last set of Covid restrictions lift on July 19.
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The frozen grocer has said that more than 1,000 have been pinged by the NHS app, causing some branches to shut.
Iceland's managing director Richard Walker said around 4% of its workforce are currently off work due to Covid, the Manchester Evening News reports.
M&S has also warned of potential staff shortages due to an increase in people being pinged by the track and trace app.
The boss of Marks and Spencer, Steve Rowe, said by mid-August as many as one in five supermarket workers could be in home isolation.
The number of test and trace app 'pings' is growing rapidly - with some branding it a 'pingdemic'.
"If there’s shortages we’ll have to manage it by changing hours of stores [and] reducing hours," Rowe said.
The self isolation requirement will be abolished for contacts of positive cases for under 18s and for double vaccinated adults from August 16.
The director of food and sustainability at the British Retail Consortium, Andrew Opie, said: "The ongoing 'pingdemic' is putting increasing pressure on retailers’ ability to maintain opening hours and keep shelves stocked.
"Government needs to act fast. 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.
"With community cases soaring, the number of healthy retail staff having to self-isolate is rising fast, disrupting retail operations."
