The NHS is "running to stand still" in its attempts to employ enough nurses, the Royal College of Nursing has warned.
Trusts were asked about staffing numbers
The 2003 data, published by the Office of Manpower Economics, showed one in 10 nurses left the NHS.
There are around 400,000 nursing staff in the NHS, which would suggest around 40,000 left.
The Royal College of Nursing (RCN) said the government had to improve measures to keep nurses in the NHS.
The OME's workforce survey for nursing staff, midwives and health visitors asked all NHS trusts in England and Wales to submit information on staffing.
It found that the "wastage rate", the number of staff leaving excluding transfers to other trusts, was 9.8%.
This was slightly higher than in 2003.
The number of newly qualified nursing staff joining was 10%.
Beverly Malone, RCN general secretary, said: "We are still running hard to keep still.
"Whilst there is encouraging news with increases in more students joining the profession, 25% of our most experienced nurses will be eligible for retirement in the next five years.
"We believe the true UK vacancy figures is around 25,000.
"These shortages have serious impacts on the quality of patient care and adds extra pressure on the existing nursing staff working in an overstretched NHS."
Overseas nurses are helping to fill the gap in nursing numbers.
The RCN believes they now account for around one in four nurses in the NHS.
The RCN says, while progress is being made in attracting new recruits to the NHS, more needs to be done to help nurses stay in the health service, particularly for those who need to combine working with a family life.
It said even something as simple as not changing nurses' shift patterns each month, as often happens now, would help.
Dr Malone said: "Sensible, robust solutions such as better pay and career development and more family friendly flexible working policies are the only way forward in making any difference in resolving nursing shortages."
But a Department of Health spokeswoman said: "There are more nurses and fewer vacancies in the NHS than ever before. 67,500 nurses have joined since 1997, and we had the largest ever increase - 19,000 - last year.
"With a workforce of 1.3 million, it's inevitable that there will be some staff turnover.
"However, we have a wide range of initiatives to encourage staff to remain in the NHS. This is reflected in the fact that since 1999 17,500 nurses, midwives and health visitors have returned to work in the NHS after a career break."