A health trust boss has warned that an "accelerating financial disaster" could hit patient care and cripple hospital budgets next year.
In an article for the Guardian, Christopher Smallwood, chairman of St George's Hospital Trust in London, says the financial burdens could leave NHS employees unpaid in 2016.
Mr Smallwood claimed hospitals were short of staff and unable to meet waiting time targets for cancer and A&E care due to years of underfunding.
He also accused ministers of being "in denial" when it came to the seriousness of the situation, describing Health Secretary Jeremy Hunt's request that the NHS delivers £22bn of efficiency savings by 2020 as "for the birds".
A spokesman for NHS England said: "Each year the NHS faces greater demand on its services and it continues to successfully look after this growing number of patients.
"But there are real pressures and we must strengthen for the future which is why the NHS has produced a plan for change.
"We must deliver that plan, using more joined up models of care, backed by the correct funding settlement, as set out in the NHS's five-year forward view."
The Department of Health defended the NHS as one of the safest health care systems in the world. It said it believed in the values of the NHS and highlighted a £10bn investment for its plan for the future.
A spokeswoman said: "There is no denial that the environment is tough but the NHS must deliver its side of the plan with cost-controlling measures like clamping down on rip-off staffing agencies and expensive management consultants.
"Last year, the NHS was ranked as the safest health care system in the world by the Commonwealth Fund and although the NHS is busy, it has been preparing for winter for months and services are ensuring patients get treated quickly."
The A&E waiting time standard of four hours - from arrival through to treatment admission or discharge - currently sits at 94.6%. The target is 95%.
Between last November and February, the service dealt with 190,000 extra A&E attendances - or a rise of 3% on the previous year.
Mr Smallwood predicted the NHS may struggle next year.
He said: "The NHS is heading for a real smash. Hospitals are at 100% capacity at the moment and the onset of winter could be a nightmare."
Professor Chris Ham, chief executive of the King's Fund health think-tank, backed Mr Smallwood's views.
He told The Guardian "everyone involved in the NHS" would see his views as an accurate representation of the problems.