WAITING times in under-pressure A&E departments last month were the longest since records began.
Just 84.6% were seen within four hours overall, falling to 76.4% at major A&E departments.
Hospitals have struggled this winter with particularly cold weather, including heavy snow, along with high rates of flu and norovirus.
Dr Nick Scriven, president of the Society for Acute Medicine, said: "These stark figures - including a further drop in A&E performance and 5,000 delayed patient transfers - are the clearest indication yet of the eternal winter we now face in the NHS, and this should be a turning point in how we approach all planning from now on".
The numbers mean the NHS in England has recorded its four worst ever figures for its key A&E target in the last four months.
The number of patients who had to wait more than 12 hours for treatment triples in a year, the latest figures for England show.
Waiting times for planned treatment have also failed to meet targets for the last two years, with 87.9% of patients starting treatment within 18 weeks.
With freezing winter temperatures resulting in unprecedented demand at A&E departments, some hospitals had to cancel planned operations in order to prioritise emergency care.
Senior vice president of the Royal College of Surgeons, Ian Eardley, said it was "completely unacceptable" that worst-affected areas had seen cancer operations cancelled.
Janet Davies, chief executive of the Royal College of Nursing, said "what began as a "winter crisis" in the NHS is now becoming entrenched".
"We need urgent answers as to why it has more than trebled in the previous year", she added.
An NHS England spokesman said: "As expected, these figures for a month ago confirm what was widely reported at the time, namely that during March the NHS continued to experience severe winter pressures".
Ian Dalton, head of NHS Improvement, said: 'April tends to mark the point where pressures start to decrease, but we can not be complacent'.