The Royal College of Nursing (RCN) sent requests under the Freedom of Information Act to all acute, mental health and community NHS trusts in England, as part of its Frontline First campaign against job cuts.
Almost a quarter (24%) of trusts responded. Of these, the average vacancy rate of 6%; in some trusts it was as high as 16%.
The union claims this "hidden workforce crisis" could have serious consequences for the NHS.
Figures from the RCN report, Running the red light, found while official numbers show the NHS in England has lost 3,859 full-time nurses, midwives and health visitors since May 2010, the scale of the understaffing problem is far larger.
Wake-up call
RCN chief executive Peter Carter said the report should act as a "wake-up call".
"We sit on the verge of a hidden workforce crisis that desperately needs addressing to ensure the NHS runs properly and patients get the care they deserve,” he said.
The report also highlights a 15% cut in the number of nursing student places commissioned since 2010-11, and forecasts a shortage of 47,000 registered nurses by 2016.
“Unsafe staffing levels have been implicated in a number of high-profile investigations into patient safety," said Carter. "We call on employers in the NHS to put an end to boom and bust workforce planning and develop clear standards to ensure safe staffing levels are met, supported by robust inspection based on reliable data."
The RCN has outlined a list of urgent priorities for achieving safe staffing in NHS services today, and called for long-term planning to secure a workforce fit for the needs of tomorrow. The priorities include mandatory workforce planning, robust systems of review and better working practices.
