Public services are resorting to emergency plans to mitigate staff shortages caused by the Omicron variant of coronavirus.
At least six hospital trusts have declared critical incidents – where priority services may be under threat.
Boris Johnson said on Monday that he would “make sure that we look after our NHS any way that we can”.
And the Education Secretary said schools should be prepared to merge classes into large groups if staff levels dipped too low.
But health leaders warned the health service was “in a state of crisis”, and a headteacher predicted remote learning could return if school staff were struck down with the virus.
The Daily Telegraph reported that up to 10 million “critical” workers would be able to access Covid tests through their employers, after days of complaints that they could not be ordered online and stocks in pharmacies were patchy.
The newspaper said health, education, transport and utilities workers would be included in the scheme, which could be announced as early as this week following a meeting of Cabinet’s Covid Operations Committee on either Tuesday or Wednesday.
But in the meantime Chris Hopson, chief executive of NHS Providers, which represents health trusts, said “a number of trusts across country have declared internal critical incidents over the last few days”.
One of those was United Lincolnshire Hospitals NHS Trust, where “extreme and unprecedented” staff shortages were expected to result in “compromised care”.
And chief executive of University Hospitals of Morecambe Bay, Aaron Cummins, confirmed in a statement that the trust had declared an “internal critical incident”.
In an internal message from Mr Cummins shared on Twitter, he told staff that “sadly, despite everyone’s best efforts, many of our patients are still receiving a level of care and experience that falls below the level of standards we would like”.
Meanwhile, Geoff Barton, general secretary of the Association of School and College Leaders, said: “It’s hard to imagine that if the NHS is being affected, that retail is being affected, if sporting fixtures are being affected, it’s hard to see why you wouldn’t in schools and colleges have the same issues around staff shortages.”
Bin collections and train services have also been hit.
A further 157,758 lab-confirmed Covid-19 cases were recorded in England and Scotland as of 9am on Monday, the Government said.
Scotland saw its highest number of daily cases yet, while numbers for Wales and Northern Ireland had not been reported on Monday night.
The Government also said a further 42 people had died in England within 28 days of testing positive for Covid-19.
Separate figures published by the Office for National Statistics show there have now been 174,000 deaths registered in the UK where Covid-19 was mentioned on the death certificate.
On a visit to a vaccination centre on Monday, the Prime Minister said he appreciated the pressure staff were under, and that it was “vital that we make sure that we help them by trying to contain the pandemic” by getting vaccinated and following plan B measures.
Speaking at the Guttman Centre at Stoke Mandeville Stadium in Aylesbury, Buckinghamshire, he warned it would be “absolute folly to say that this thing is all over now bar the shouting”.
But he also said it was “very encouraging” to see children getting jabbed before going back to school.
Speaking to staff, Mr Johnson remarked on people of “all ages” queuing up to get a vaccine.
“Loads of kids too, it’s very encouraging to see. All the kids getting jabbed before they go back to school,” he said.
It comes as some pupils return to the classroom on Tuesday with new advice to wear masks in the classroom.
The move has been recommended for secondary school pupils in England, alongside testing twice a week.
Education Secretary Nadhim Zahawi said: “What we’re saying is, look, with Omicron, because it’s so infectious, we want to make sure that we give you as many tools to be able to make sure that education is open.”
But he admitted it was “more challenging, of course, to deliver education with masks on in the classroom”.
He said: “This is an aerosol-transmitted virus and if you’re wearing a mask, if you’re asymptomatic, then you’re less likely to infect other people.”
Mr Johnson admitted he was not happy about the plans but said they were necessary for now.
It is hoped the return of masks may prevent the need to disrupt children’s education further.
Mr Zahawi said: “The most important thing is to keep them (schools) open.
“We monitor staff absenteeism, I just said to you we’re running at about 8% last year. If that rises further then we look at things like merging classes, teaching in bigger numbers.”
Plan B measures to tackle coronavirus are set to be reviewed when MPs return to Parliament on Wednesday, when the Prime Minister will likely also face questions about reports in the Daily Mirror that he failed to self-isolate in January last year after coming into contact with a staff member who tested positive.
A Downing Street spokesperson told The Mirror Mr Johnson had been socially distanced from the staff member and was in their company for less than 15 minutes.
The spokesperson said: “He was not advised to isolate as the rules did not require him to do so.”