The Ombudsman will investigate the Hospital Authority's free ambulance-transfer service, which shuttles ill people between home, clinics and hospitals, after receiving a spate of complaints about it. Each year the service serves more than 350,000 patients who need a stretcher, wheelchair or continuous supply of oxygen to be moved. But Ombudsman Alan Lai Nin said his office had received complaints that revealed 'a fundamental problem' in its operation. He said the authority grouped patients' requests by routes and times for maximum efficiency and this led to uncertainty for patients. 'Patients with bookings cannot be sure whether and when they can get the service on the day. The waiting time is uncertain and the course of the trip can be circuitous,' he said. 'Unsatisfactory service apart, the patient may miss medical appointments or have to spend extra time in hospital.' Among the complaints was one from a patient who had to wait an hour or longer for every trip to attend or leave a clinic. Another patient, who booked the service for his discharge from hospital, found only in the late afternoon of that day that no ambulance was available, Lai said. A direct investigation would look at three areas: the booking and scheduling system, the mechanism for monitoring the service, and areas for improvement. An authority spokesman said it welcomed the investigation and would co-operate fully with the Ombudsman's office. 'The supply and demand of the service is under close monitoring by the authority,' he said, adding that it would constantly review service quality to meet increasing demand. The authority runs 133 non-emergency ambulances, with 367,182 patients using the service last year, slightly up on 350,963 in 2008. Outpatients who attend day clinics by appointment and inpatients being transferred between hospitals or being discharged can apply for the service. Patients make requests through clinical staff in hospitals. The authority says bookings for transfers are made according to the next medical appointment to ensure that the service will tie in with the follow-up consultation. Patients' Rights Association spokesman Tim Pang Hung-cheong said the problem was that resources were not sufficient to meet the growing demand.