Demand for critical care beds is outstripping supply despite a rapid growth in bed numbers, an Audit Commission report has found.

Nine out of 10 acute trusts now have an intensive care unit and the average number of beds rose from four to six between 1993 and 1998.

Despite this investment - the NHS in England and Wales now spends£700m a year on critical care and costs are rising by 5-10 per cent a year - staff interviewed for the report said they have to turn away or discharge patients early at peak periods.

That has led to calls for more beds but the report says supply-side solutions are 'unlikely to work on their own' since 'supply can generate demand, resulting in further pressure'.

It says improving care on wards could prevent some patients deteriorating to the point of needing critical care, a view endorsed by Wilma McPherson, director of nursing and quality and chair of the critical care advisory board at Guy's and St Thomas' Hospital trust.

But she warned that the range of ICUs and patients admitted to them meant 'it cannot be applied right across the country'.

The report says trusts need to plan discharge from ICUs and carry out regular audits of patients receiving critical care. Some may be inappropriately placed in ICUs towards the end of their lives, while others 'may be too well to justify the higher staffing levels and expensive equipment'.

The report makes similar points in relation to high-dependency units.

Co-author Dr Richard Waite endorsed the idea that they can be 'a step down' from intensive care 'from a quality point of view' but warned that 'people can be sucked in to fill beds'.

The report says an average ICU has five direct care nurses on duty at any time, but some units use twice as many nurses to achieve this as others.

Dr Paul Lawler, immediate past president of the Intensive Care Society, said 'reasonable organisation and managerial changes' suggested in the report could not be implemented immediately.

But without intensive care facilities, proposals to improve cancer and cardiac services 'will not be easily achievable'.

Critical to Success . Audit Commission Publications, 0800-502 030.£20.