Chris Hopson, the chief executive of NHS Providers, said staff were working “flat out” and that the government “must be ready to introduce new restrictions at pace if they’re needed”.
The latest data released on Saturday showed England had broken another record for the number of daily Covid cases.
Figures also showed that hospital admissions in England have risen to their highest level since January 2021, while the number of NHS hospital staff absent due to the virus has nearly doubled in a month.
Mr Hopson, the chief executive of NHS Providers, which represents health trusts, tweeted that the health service was “preparing for worst & hoping for best”.
“Staff flat out, esp. given level of staff absences. We will need to ask them to perform flexible heroics again if hospital covid numbers continue to rise,” he wrote.
”We can’t keep doing this. Long term NHS capacity issues must be addressed.“
A new record of 162,572 Covid cases has been registered in the past 24 hours in England, government figures showed.
The number is up from the 160,276 new lab-confirmed Covid cases in England in the previous 24-hour period reported on Friday.
The figure does not include cases in Scotland, Wales and Northern Ireland, which have not been published.
A further 154 people died in England within 28 days of testing positive for Covid-19, Saturday’s figures showed.
It came after Sajid Javid, the health secretary, warned restrictions on freedom ”must be an absolute last resort“.
NHS England data showed 24,632 staff at NHS hospital trusts were ill with coronavirus or having to self-isolate on Boxing Day, up 31 per cent from 18,829 a week earlier and nearly double the 12,508 at the start of the month.
Mr Hopson wrote: ”Govt must be ready to introduce new restrictions at pace if they’re needed.
“Positive news is that we are still not seeing the large numbers of severely ill older people that we have seen in previous peaks. Vaccine effect very pronounced.”
He added that it was still unclear how London, which has been at the centre of the Omicron wave, would fare in the days ahead.
Mr Hopson wrote: “Striking general view that future London trajectory remains very unclear. Significant uncertainty. All options open. From hospitalisations will shortly plateau and then start to drop. To increases grow rapidly post Xmas. And all points in between. Planning v difficult!”
Dr Chaand Nagpaul, BMA council chairman, said it was “wholly erroneous to talk about the risk of the NHS becoming overwhelmed”, adding that the new year began with the NHS “already overwhelmed, in a parlous state, and with patient care suffering”.
He described staff as “exhausted”, and added: “A key priority for the Government this year must be to properly invest in doctors’ wellbeing, recognising that the NHS cannot afford to lose any more of its workforce without dangerously jeopardising patient care.”