By Caroline Ryan
BBC News Online Health Staff in Harrogate
The NHS is in a "race against time" to replace the 50,000 nurses who will retire over the next five years, a nursing leader has warned.
Many wards are still overstretched says RCN
Official figures show the NHS has recruited 40,000 extra nurses since 1997.
But Dr Beverley Malone, general secretary of the Royal College of Nursing, said that without an influx of international nurses in recent years the health service would be "running to standstill".
Dr Malone issued her warning at the union's annual Congress in Harrogate.
The RCN says overseas nurses are only a short term solution, and efforts need to be made to recruit staff who will remain in the NHS for years to come.
Dr Malone said: "The nursing shortage still represents a real threat to patients.
"We're calling on the government to keep up their efforts to recruit more nurses, and to work even harder to retain those we already have."
The RCN has warned many hospitals still face difficulties in filling vacancies, and Dr Malone warned that only the "aggresive" recruitment of nurses from overseas had prevented a breakdown in the health service.
She said the NHS was still heavily reliant on agency nurses, with spending trebling in England over the last seven years, reaching £529m last year.
The RCN's warnings are based on the findings of two surveys it commissioned.
An examination of the UK nursing market found the number of registered nurses would not have increased from 1998-99 to 2002 would not have increased without the growth in the number of overseas nurses.
And a snaphot survey of 46 UK trusts found, on average, wards had 20% fewer than the number the trust said they needed - if factors such as maternity and long term sick leave were taken into account.
The RCN estimates the three-month vacancy rate was around 8% - almost three times the government's estimate.
And medical wards reported having the equivalent of just one extra nurse compared to 1998, despite the extra nurses the government claims to have recruited.
On average, wards 10% of staff were bank and agency nurses.
Dr Malone told the conference the new pay system Agenda for Change, set to be introduced at certain sites later this year, was key to recruiting - and retaining - new staff.
The radical restructuring has been designed to ensure the most skilled nurses receive the highest pay.
She said: "The NHS has been given a tremendous cash boost in recent Budget allocations. But the money has to show up where it will benefit nurses and patients.
"Investing in staff is investing in patient care, so it's right that a significant proportion of the extra resource is being used to recruit and pay the health care workers that patients and communities need."
Just over half of those trusts surveyed by the RCN said there were too few qualified nurses on the ward, with around the same number reporting the skill mix was wrong - so they did not have enough of the right kinds of staff.
When asked what effect these problems had, nurses said they caused stress and low morale and meant they could not meet all their patients' needs.
The RCN says nurses who have left the profession, or are considering leaving, commonly site those three reasons for leaving.
It said part of the reason for the skill mix problem could be that most new entrants to the NHS, and international nurses, come in at the lowest grades.
But those who are leaving are the most senior staff leaving gaps that are difficult to fill.
Some specific professional groups, like district nurses, have seen their numbers fall.
Evan Harris MP, Liberal Democrat health spokesman, said: "The government may boast about their recruitment success. But what really matters is the level of care that patients receive.
"Patients at present have trouble getting into a bed at all, and then are faced with overworked nurses trying to do their best in very difficult conditions. This is the biggest problem facing the NHS today.
"We don't just need to recruit more nurses, we need to recruit the right nurses in the right specialities and with the right experience."
A Department of Health spokeswoman said: "The number of nurses working in the
NHS is increasing and is at an all-time high with more than 40,000 extra nurses
"We are on track but more work needs to be done if we are to reach the target
of 80,000 more nurses by 2008 compared to 1997.
"Agenda for Change will reform pay and working practices and help to keep
recruits on track.
"We are also retaining staff through the Improving Working