Saffron Cordery, deputy chief executive of NHS Providers, said the NHS is also now dealing with “significant” staff absences.

“We are already seeing NHS staff shortages in hotspots like London, with worrying increases in the number of staff having to take time off work due to Covid-19 self-isolation or sickness,” she said.

“This is expected to rise in the weeks ahead. The impact on the workloads of remaining staff – who are already working incredibly hard given the huge demands on the service – is a major concern.”

Chris Hopson, chief executive of NHS Providers, told BBC Radio 4’s PM programme on Saturday that Covid cases in London hospitals are around 1,500 – up 30 per cent in a week, compared to a national average of four per cent.

But he added: “It’s not just the increase in Covid caseload that’s a problem, it’s also the fact that we’ve got staff absences going up.

“So if you look at London, NHS staff absences, they’re up 140 per cent, from 1,900 on Sunday to 4,700 on Thursday, so it’s gone up very dramatically, very quickly.”

NHS Providers, which represents NHS leaders, said it has been calling for a fully-funded workforce plan long before the winter.

“Without the right staff in the right places with the right skills, we knew the pressures on the NHS would be difficult this winter,” Ms Cordery said.

NHS ‘brutally exposed’ to rising omicron case rates

Dr Chaand Nagpaul, British Medical Association council chairman, said the NHS has been left “brutally exposed to suffer the consequences of surging case rates,” without additional restrictions in place.

“Amid the surging case-rate, driven by the hugely transmissible omicron variant, doctors are not only incredibly worried about the potential impact this could have on hospitalisations, but also about what it would mean for patient care across the NHS if we have vast swathes of staff off sick with the virus,” he said.

“We’re already seeing services being affected by staff absences, and these estimates show it could get far, far worse.”