Record numbers of people called NHS 111 over the festive period and there was a sharp rise in ambulances being delayed outside accident and emergency units.
The data, from NHS England, covers the week ending 31 December.
More than 480,000 people called NHS 111 – a 21% rise on the previous week.
Ambulance crews faced delays of over 30 minutes handing over patients to A&E staff nearly 17,000 times during the week – a rise of over 40% on the previous week.
The figures suggest the NHS was incredibly busy during the festive period, explaining why there have been so many problems this week.
At least 20 hospital trusts have had to declare major incidents this week – about one in eight of the total.
The pressures prompted NHS England to order the cancellation of tens of thousands of non-urgent operations until the end of January in an attempt to ease the pressure on hospitals.
The move prompted Health Secretary Jeremy Hunt to apologise to patients.
Non-urgent treatments had already been cancelled until mid-January, but NHS England said on Tuesday that would now be extended to the end of the month.
It came after hospitals reported they were struggling to cope with the surge in patients being seen since Christmas.
At least 20 hospital trusts – one in eight – have declared a major incident this week, the BBC understands.
Bosses said they had been pushed into the move as patients were experiencing long waits in A&E and being left on trolleys in corridors because there were no beds available.
Some ambulance services have even started asking 999 callers with less serious problems to make their own way to hospital so they can prioritise the most life-threatening calls.
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Problems have also been reported in other parts of the UK.
The Welsh government said the health service was facing “significant pressure”.
Meanwhile, in Scotland there has been a 20% jump in A&E attendances compared with the previous year, prompting an increase in patients waiting more than four hours, and in Northern Ireland the Antrim Area Hospital has had to bring in St John Ambulance volunteers to help with a surge in demand.
NHS England’s Prof Keith Willett admitted the pressures were severe – the worst he had seen since the 1990s – but denied there was a crisis, as plans were in place to help hospitals.
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