Staff shortages, recruitment freezes and redundancies are putting the NHS under "severe pressure", according to a report by the country's largest public sector union.
Unison said a survey of more than 8,000 staff showed that the government's squeeze on public spending was "dragging" the health service back to the 1980s and 90s when the NHS was "starved" of funds.
Unison said its study revealed a frontline under pressure, with four out of five of those questioned saying their workload had increased and most reporting a decline in staffing levels.
Karen Jennings, Unison's head of health, said: "Government cuts threaten to undo and reverse the benefits of all the investment and hard work that has gone into turning the NHS around over the past 13 years. We have been able to train our own nurses instead of scouring third world countries to fill shortages.
"In a worrying reversal, half the people we surveyed are affected by staff shortages. This is particularly dangerous because the lack of staff was a key factor in the appalling problems with patient care at Mid Staffs Hospital."
A Department of Health spokesperson said: "Better care can cost less and all over the NHS, people are making changes to improve care and save money. Together, our efficiency drive and reform proposals will create a high-quality health service that empowers staff and puts patients in control."