Fully-vaccinated critical workers have been made exempt from having to isolate over Covid contacts.

This is part of prime minister Boris Johnson's plans to ease the "pingdemic", the government has said.

NHS staff and workers in other sectors are among those who have been granted approval to avoid quarantine for crucial work reasons as Covid-19 infections soar.

In the face of widespread criticism from businesses over staff shortages, Mr Johnson announced a plan for a "small number" of critical workers to be able to continue.

But he faced calls to clarify who would be eligible, after a government statement said it would not be a "blanket exemption for any sector or role".

Number 10 was unable to say how many people the government will approve for the loosened rules, ahead of the full relaxation for everyone who is double-jabbed on August 16.

But it was not expected to reach the high tens of thousands, raising questions over whether supermarket workers would benefit.

The prime minister's official spokesman said: "The first exemptions I understand have already been given in some critical sectors, that work is going on given the urgency. That's in both wider sectors and the NHS as well."

He said employers should contact the suitable government department to request exemptions.

"It's not a blanket exemption and my understanding is we're not going to be producing a list covering individual sectors, these business-critical areas will be able to apply for exemptions to their host departments," the spokesman said.

Asked specifically about supermarket workers, he said: "We're not seeking to draw lines specifically around who or who is not exempt.

"What's important is to make sure critical services are able to function and get that balance right between requiring people to isolate... but also making sure critical services can function."

On Monday, Mr Johnson resisted calls for a more wide-reaching change to quarantine rules to reduce the number of people in isolation, as Covid-19 cases soar.

Dereham Times: Prime minister Boris JohnsonPrime minister Boris Johnson (Image: Archant)

He said it is necessary to keep the rules largely unchanged until August 16, when a testing regime will replace the requirement for fully-vaccinated contacts to isolate.

Mr Johnson said self-isolation is "one of the few shots we have got left in our locker", on the day he scrapped most remaining legal restrictions in England.

He suggested it would cover some in hospitals and care homes, or working in the supply of food, electricity and medicines, and transport, defence and borders.

Vaccines minister Nadhim Zahawi said the change would cover the police, air traffic controllers and train signallers, and others in "circumstances where there would be a serious risk of harm to public welfare if people in critical roles are unable to go to their workplace".

But neither went further in setting out who it would apply to and a subsequent government statement said departments will be writing to employers to explain their next steps.

"This is not a blanket exemption for any sector or role. Decisions to inform an employer that designated critical workers are considered to have a reasonable excuse to attend work will be made by the relevant department with responsibility for the critical service," a spokesman said.

Liberal Democrats health spokeswoman Munira Wilson accused the government of "chaotic late-night meddling with the self-isolation criteria" that will "sow further confusion".

"The government must stop undermining all the sacrifices we've made through their continued incompetence and issue immediate clear guidance to everyone affected by these changes," she added.

The British Retail Consortium called for clarity on who would be exempt and said retail workers and suppliers should be included for the "vital role" they have played in the pandemic.

Chief executive Helen Dickinson said: "While it is good that government recognises the problems that are being created by an overzealous track and trace system, it remains unclear who will be covered under the new list of critical workers.

"With community cases soaring, the number of healthy retail staff having to self-isolate is rising fast, threatening to disrupt retail operations, and potentially close shops or distribution centres."