Retailers have warned of disruption and the Government moved to protect the delivery of essential services as a record number of people were told to isolate by the NHS Covid-19 app.

The system sent more than 600,000 alerts to users in a week, according to the latest figures, which do not cover the period since restrictions were lifted and more social contact was allowed.

Former health secretary Jeremy Hunt said the Government risks “losing social consent” for isolation if it does not immediately bring forward the relaxation of quarantine rules for the fully vaccinated.

Business Secretary Kwasi Kwarteng told shoppers not to panic in the face of supermarket shortages and attempted to ease concerns over the “pingdemic” as Covid-19 cases soar.

In guidance for England published on Thursday night, it emerged that employees providing critical services would only be able to keep working and avoid self-isolation after being identified as a contact if they were named on a list kept updated by officials.

The exemptions – mainly in 16 sectors including essential transport, food supply, emergency services and energy – will allow people identified as contacts by NHS Test and Trace or the app to carry on working if their failure to do so would have a “major detrimental impact” or risk national security.

The policy only applies to named workers who are fully vaccinated and it is not a “blanket exemption” for all employees in a sector – for instance, while railway signal operators on whom the network depends may be given an exemption, individual train drivers are unlikely to be.

The guidance is intended to operate until August 16, when a wider exemption from self-isolation will apply to fully vaccinated contacts.

Warnings of staffing shortages mounted as NHS figures showed 618,903 alerts were sent to users of the coronavirus app in England and Wales in the week to July 14, telling them they had been in close contact with someone who had tested positive.

Confederation of British Industry director general Tony Danker echoed the call, warning: “The current approach to self-isolation is closing down the economy rather than opening it up.”

Businesses have exhausted contingency plans to get in extra staff and are “at risk of grinding to a halt in the next few weeks”, he said.

Iceland’s managing director Richard Walker said the supermarket was having to hire 2,000 temporary workers to prepare for “the exponential rise in pinging”.

“The dramatic pictures that you might have seen in the media are isolated incidents and not widespread,” he told BBC Radio 4’s Today programme.

“But the people who should be panicking are the Government, and I believe that… the sooner they clear up this mess, and get retail workers and HGV drivers on to the key worker list, the better.”

The British Retail Consortium (BRC) urged ministers to “act fast” to issue exemptions, with the wider relaxation not scheduled until a month after most coronavirus laws ended in England.

That date “feels a long time away”, BRC chief executive Helen Dickinson said, as she warned stores are closing, hours are being reduced and consumers are facing reduced choice.

“I think what the most important thing for Government to do is to recognise that the current situation is untenable,” she told BBC Breakfast.

Meanwhile, officials announced a further 39,906 lab-confirmed Covid-19 cases in the UK and that an additional 84 people had died within 28 days of testing positive for Covid-19.

A lorry driver shortage was putting increased pressure on the country’s grocery supply chain and empty shelves were witnessed in some supermarkets across the country.

Mr Kwarteng had to tell businesses to “stick to the rules” after a food distribution company struggling with staff shortages advised workers who are pinged by the NHS app to take tests and continue working, in breach of Government advice.

Bidfood chief executive Andrew Selley defended his approach for delivery drivers to continue working if they have negative results as “appropriate and safe” for the “critical workers”.

“If they are pinged we ask them to take a PCR test. If that’s positive then clearly they’ll isolate, but if it’s negative we ask them to come back to work and we have a process of doing lateral flow tests daily away from their workplace, and if that’s negative they can proceed with their work,” he told Today.

Professor Ravi Gupta, a scientist advising the Government as part of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag), described it as a “mixed bag of measures which are creating confusion and havoc”.

“I think it is a little bit difficult to justify people doing self-isolation when in fact we have held huge sporting events with large amounts of transmission that have probably gone undetected,” he told Sky News.