WESTMEAD HOSPITAL is cancelling surgery at four times the rate the Health Department considers acceptable, and waiting times are so long some surgeons are refusing to add new patients to their operating lists.

About 8 per cent of elective surgery patients at the flagship Sydney University teaching hospital had their operation cancelled on the day of surgery, due to a shortage of post-surgical beds. This was often after fasting and being prepared for theatre, said John Fletcher, chairman of the hospital's surgery division.

This did not include the many patients told not to come to hospital days before their scheduled operation. Those cancellations - which Professor Fletcher said affected up to half of patients for some types of surgery - were not formally recorded.

Population growth, a jump in the proportion of emergency admissions last year from 41 to 45 per cent of all surgery, the designation of Westmead as a major trauma treatment centre, and the rigid enforcement of unrealistic bed budgets were behind the worsening shortage of beds for non-emergency surgery, he said.

Hospitals in western Sydney have suffered staff freezes and bed cuts due to debts that last year reached $26 million. Doctors insist the quality of treatment at Westmead remains excellent, but they are frustrated they cannot accept more patients.

The neurosurgeon Brian Owler said he was under pressure from managers to schedule operations that had virtually no chance of taking place on the nominated day, but had begun to refuse.

''I think it's unfair to patients when the possibility of them being operated on that date is extremely small,'' he said. ''People arrange their lives around it. They take holidays and get relatives to fly interstate to look after them.''

Associate Professor Owler, the Australian Medical Association's NSW councillor for surgeons, said many patients in so-called category 2 - whose procedure should be performed within 90 days - were waiting much longer, sometimes with disabling spinal conditions.

''People suffer pain and numbness and they can't walk,'' he said. ''If they get [high blood pressure] because they can't exercise, that compounds the problem.''

Patrick Cregan, the chairman of NSW Health's Surgical Services Taskforce, said same-day cancellations in western Sydney were about twice the state average, and much higher than the 2 per cent maximum set by NSW Health.

''The fundamental problem is that [the area] doesn't have the resources it needs,'' he said.

Peter Klineberg, chairman of Westmead's medical staff council, said the 854-bed hospital - the state's largest - was effectively capped at 17 elective surgery patients a day who would require an overnight stay.

This was in addition to gynaecology and cardiac patients who are accommodated in separate wards, and day-surgery patients. The hospital could perform almost twice as many operations if beds were available.

Under the state trauma plan released on March 1, Westmead would receive a greater proportion of severely injured patients.

Dr Klineberg said this would exacerbate bed shortages.

A spokeswoman for Sydney West Area Health Service said it was too early to know the impact of the trauma changes.

She said Westmead was meeting elective surgery targets and in the period to last December 90 per cent of patients had their operation on time.