Nursing ward staff take more sick days per year than most other public sector workers, the NHS inspectorate says.
Patient satisfaction with nurses is generally high
Figures from the Healthcare Commission, based on 135,000 staff on 6,000 hospital wards, show on average staff have 16.8 days in every 12 months.
This compares with 11.3 days a year across seven other public sector groups, including police and teachers.
The Department of Health said reducing stress and sickness among staff was an important objective for NHS trusts.
Sick leave among ward staff costs around £470m a year.
Anna Walker, chief executive of the commission, said: "These high rates of absence among nurses are extremely worrying.
"Whatever the reasons for them, nurses are far too important for us to ignore this problem."
Ms Walker said the causes were unclear, but factors such as stress, job satisfaction, work load and the physical nature of the job all may be part of the picture.
The report found in general that patients are satisfied with nursing care - though there is markedly higher satisfaction in specialist trusts and lower satisfaction in London trusts.
However, patient satisfaction levels were inversely proportional to reliance on temporary staff.
In particular, patients expressed dissatisfaction in the ability of nurses to answer their questions.
The report found that 13.2% of ward staffing expenditure was spent on bank and agency staff in the first quarter of 2004/05, a similar figure to 2000.
Ms Walker said: "The use of temporary staff across NHS hospital wards remains stubbornly high.
"Trusts need to focus on recruitment of permanent staff to reduce dependence on temporary staff.
"While labour market forces are important, we have found considerable variation in vacancy levels between trusts - even those within the same region.
"Some trusts are better at recruiting and retaining and it is important that good practice in this area is gathered and shared throughout the NHS."
Dr Beverly Malone, general Secretary of the Royal College of Nursing said huge demands were being placed on ward staff.
"With such a high workload it is not surprising that so many nurses are sick due to stress.
"RCN research has also shown that sickness absence is often caused by work place injuries including needle stick injuries and severe back strain.
"We would like to enforce the report's key finding that 'employing more experienced and skilled staff in the workforce does have a positive impact on the care of patients.'
"An excellent illustration of how more nurses make a difference is that fewer pressure ulcers develop in hospitals where the proportion of registered staff is relatively high.
A Department of Health spokesman said it was working to ensure staff had access to flexible working patterns, childcare provision and occupational health services.
"We are aware that a high turnover of temporary staff does not provide continuity of care for patients and we are encouraging the NHS to reduce the use of agency staff by improving working lives and investing in training and recruitment."
Alastair Henderson, deputy director of NHS Employers, said: "Employers are not relying on temporary staff as a matter of preference but because of difficulties, in either the short or longer term, in employing sufficient permanent staff.
"In that position it is better for patient care to be employing temporary staff rather than no staff."