Supermarket supply chains are "starting to fail" because the "pingdemic" is sending thousands of workers into self-isolation, food industry leaders warned on Wednesday night.
Shop shelves in some areas were empty of basic supplies, while petrol stations ran out of fuel as the NHS Test and Trace app threatened to bring parts of the economy to a standstill.
MPs and industry leaders urged the Government to ease the growing crisis by including supermarket staff, lorry drivers and other frontline workers on a list of those exempted from automatic self-isolation when 'pinged' by the app as a contact of someone with Covid.
The Government has yet to publish guidance on which industries would benefit from any exemption scheme. A list was expected on Wednesday but no announcement came.
In the Commons, Boris Johnson apologised to affected businesses for the "inconvenience" but urged them to stick by the rules and support workers to stay at home.
It came as the "pingdemic" wreaks growing havoc, with more than half a million people pinged by the app in a single week.
The police and crime commissioner for Cleveland warned the public to expect longer response times to calls, while Royal Mail announced delays to deliveries in 10 parts of England after an increase in absences caused by self-isolating staff.
Supermarket leaders said an existing national shortage of lorry drivers had been brought to near-crisis point by the numbers sent into self-isolation by the app.
Shelves were empty of supplies including bread, meat, fruit and vegetables in parts of Bristol, Cambridge and Southampton.
Tesco said it had run out of bottled water in its warehouses as the country swelters in a heatwave, while the Co-op said supplies in "a large majority" of its stores had been disrupted "due to the impact of Covid/isolation of colleagues".
A spokesman said: "This is a short-term but significant impact and has impacted our ability to supply stores. These issues are impacting a large majority of Co-op stores."
Iceland announced plans to draft in 2,000 temporary employees to keep stores open.
Nick Allen, the chief executive of the Meat Processors Association, warned that the supply chain was at risk of collapse, saying some of his members had lost up to 10 per cent of their workforce to self-isolation.
"There's an air of despondency creeping through the industry really," Mr Allen told the BBC. "Until now we've managed to
keep the food supply chain running, but there's a sense of we're starting to fail on that front."
Asked whether production lines were stalling, he said: "They are. It's happening already. We're starting to see that at retail
level and in restaurants – everyone is struggling to get things out."
MPs and industry leaders called on the Government to include supermarket workers and lorry drivers in an exemption scheme allowing "critical" workers who are pinged to return to work after a PCR test and do daily lateral flow tests rather than self-isolating for 10 days.
Andrew Opie, the director of food and sustainability at industry lobby group the British Retail Consortium, said the Government needed to act swiftly to tackle the problem.
"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," he said.
Lorry drivers were already in short supply before the "pingdemic", with the Road Haulage Association estimating a shortfall of about 60,000, caused in part by cancelled driving tests.
Rod McKenzie, of the association, said the Government's plan was "confusing" and felt like "it's been rushed", adding: "Where do you draw the line on lorry drivers, essential workers, the people in the supply chains? Because most of the people I know in the supply chain would say 'hang on a sec, I'm an essential worker'."
Earlier this week, the Government said there will be no list of critical workers exempt from isolating rules and exemptions will be "considered on a case-by-case basis".
On Monday, Mr Johnson indicated those that would benefit included "our hospitals and care homes, the supplies of food, water, electricity and medicines, the running of our trains, the protection of our borders and the defence of our realm". This was on top of NHS staff.
However, on Tuesday the Government published no guidance on exactly which industries would benefit from the exemption, how companies hoping to take part could apply or what criteria would be used to judge applications. Firms are told to contact the relevant government department.
A list of which sectors would be allowed to take part in the scheme was expected to be published by the Government on Wednesday, but by early evening no announcements had been made.
Sources in the Department for Business, Energy and Industrial Strategy said it had been inundated with requests about the exemption from companies amid confusion about the scheme and business frustration at the impact of the "pingdemic".
Government figures from Mr Johnson down, have stressed repeatedly that the exemption is only designed to be used for a "very small" number of people on whom the nation's "critical" infrastructure depends. One well-placed Whitehall source indicated that tens of thousands, rather than hundreds of thousands, could benefit.
"It was made very clear to us that this exemption will be for very, very few people," said Mr Allen. "They described it as setting the bar very, very high, and we're certainly not counting on that."
Meanwhile, it emerged that NHS staff can refuse to return to work even if they are given an exemption from self-isolation requirements. A letter from Prof Stephen Powis, the NHS medical director, to NHS trusts on Monday warned they had the "right to allow", not to "compel", staff to return to work.
Industry sources warned that even if supermarket workers are exempted some may be incentivised to stay in self-isolation by the £500 Test and Trace Support Payment handed to people on low incomes.
Meanwhile, Downing Street said that engaged couples pinged by the app on the night before they are married should call off their weddings. Downing Street backed Vicky Atkins, the Home Office minister, who said brides and grooms had to stay at home if they were told to self-isolate.
Mr Johnson, self-isolating at Chequers and taking part in Prime Minister's Questions remotely, said: "I apologise to everybody in business up and down the land and in all kinds of services, public sector or otherwise, who are experiencing inconvenience."
He urged people to follow the rules until August 16 when the country shifts to "a system based on contact testing, rather than contact isolation", adding: "Until then I must remind everybody that isolation is a vital tool in our defence against the disease."
Cleveland police and crime commissioner Steve Turner said: "We suddenly find ourselves cancelling rest days and cancelling leave and bringing officers in from other shifts to cover where we have got the gaps. However, our call times will go up, we will miss some calls we would normally pick up because we have less resilience in the call centre."
In Dorset, a third of control room staff were off work after being pinged or tested positive.
BP said shortages of unleaded petrol and diesel had seen a "handful" of its UK sites close temporarily after a distribution centre was closed due to staff shortages last week but added that the "vast majority" of shortages were being "resolved within a day".