The Hospital Authority also announced on Thursday that it would audit private medical services bills at Queen Mary Hospital for the past three years.

Authority chairman Anthony Wu Ting-yuk said yesterday that the authority was concerned about billing complaints and would co-operate with the university's inquiry.

Sources close to the investigation said 'irregular' billing was made known to various parties, including Queen Mary Hospital and the Hospital Authority, late last year. University doctors can see private patients according to gazetted rates. There are 10 levels of charges depending on an operation's complexity.

The charges range from HK$3,900 to HK$8,000 for a 'minor I' operation, to between HK$70,000 and HK$300,000 for an 'ultra-major III' operation. The incomes are shared between the university and the Hospital Authority on a 75 per cent and 25 per cent share.

Sources said 'deflated' charges were put on some patients' official bills handled by the hospital administration. Internal audits have checked some patients' medical records and found that classifications of operations on their official bills were 'inconsistent' with the care descriptions in medical records.

For example, for a patient who should have been charged HK$100,000, only HK$10,000 was put down on the official bill.

'The committee of inquiry has to find out whether in such a case, the patient has been charged separately for the remaining HK$90,000? If the answer is yes, where has the money gone? Does it go to the university, the faculty or individuals?' one source said.

The practice of 'irregular billing' has been going on for some time and the hospital has asked the university more than one time for an explanation. The university eventually agreed to set up the committee of inquiry on January 27 after more and stronger allegations were made.

A medical source said the government was also eager to have the incident settled by the university as soon as possible to minimise the damage to public health care.

The university announced on Wednesday that its dean of medicine, Professor Lam Shiu-kum, had tendered his resignation for 'personal reasons'.

The faculty board held an emergency meeting yesterday to brief about 60 staff members on the latest situation.

Faculty board chairman Professor Chow Shew-ping said yesterday that Professor Lam stood by his resignation when they spoke on the phone on Monday.

Another medical source said that although there were clear guidelines on operation charges, depending on their complexity, an audit of operation classifications would be difficult.

'It is a highly professional matter and only the doctor who conducted the procedure knows exactly how complicated it is. It is difficult for a layman to do so, but some experienced doctors who cross-check the bills and the medical records may get some clues.'

The committee of inquiry, chaired by Executive Councillor Leong Che-hung, will submit a report within three months.