Ambulances completed 93,500 handovers at hospitals last week – the most so far this winter.
Respiratory virus admissions were rising and NHS 111 call handlers also saw their busiest week yet.
Professor Julian Redhead, NHS England’s national clinical director for urgent and emergency care, said demand always increased during the post-Christmas period but this was worsened by junior doctors’ three-day walk-out in December.
Members of the British Medical Association are now in the middle of another six-day strike, timed to cause maximum disruption.
Professor Redhead said: “Although we have extensive preparations in place for strikes, and emergency care will continue to be prioritised, there is no denying the NHS has started the year in a very difficult position.
“This latest round of strike action will not only have an impact on this week but will have an ongoing effect on the weeks and months ahead, as we struggle to recover services and cope with heavy demand.”
The number of patients on wards with flu had increased by a third in seven days, to an average of 1,313 in the week to New Year’s Eve.
Numbers with Covid were up 8% in a week to 3,929. Some 81 sufferers were in intensive care – a 70% jump in seven days.
However, the number of people in hospital with norovirus-like symptoms had decreased from 452 to 378 week-on-week.
Despite the pressure, there were signs the NHS is coping slightly better this winter than last year.
Some 24,384 hours were lost to ambulance handover delays last week, but this was less than half the figure during the same period in 2022.
An average of 11,478 patients remained in hospital despite being medically fit to be discharged, down from 12,809 a year earlier.
And adult bed occupancy stood at 91% – the lowest it has been so far this winter, following efforts to discharge more patients before Christmas.
Professor Redhead added: “The pressure is not going to let up any time soon, with four more days left of the longest ever consecutive strike action taken in the history of the NHS, and flu season not expected to peak in the near future.”
Sir Julian Hartley, NHS Providers’ chief executive, said the “double whammy” of walk-outs on top of sustained pressure was creating a perfect storm.
He added: “The effects of a six-day strike by junior doctors this week, hard on the heels of a three-day stoppage before Christmas, will be felt right across an already hard-pressed NHS.
“The government and unions must act fast to settle this long-running dispute and prevent more walkouts for the sake of patients and staff.”
More than 1.2 million appointments have been rescheduled since strikes by NHS staff began just over a year ago.
Shadow chancellor Rachel Reeves urged ministers to resume talks with junior doctors to “get the NHS off the floor”.
She said: “NHS waiting lists are now at 7.8 million, half a million higher than when Rishi Sunak said he was going to reduce them.
“The Government need to get back round the negotiating table with junior doctors and others in the NHS so that we can get the NHS off the floor and be there once again to support patients.”
