The authority yesterday held a high-level meeting to discuss reforming its on-call system, which involves about 2,000 senior doctors. The authority will hire a consultant to calculate exactly how much it is liable to pay out because of Tuesday's ruling.

Several medical professionals familiar with the situation said doctors' claims for time spent on call could be more than HK$300 million.

In March 2006, a lower court ruled that public doctors could only claim compensation for time actually worked on rest days, public and statutory holidays, and that they could not be compensated for working overtime.

After that ruling, the authority offered a HK$629 million settlement to 4,600 doctors. About HK$500 million has been paid out so far. More than 200 of the doctors refused to settle and 100 decided to fight the case.

The doctors who accepted the settlement in 2006 can now claim compensation for days spent on call since then. Doctors who refused to settle can claim for the six-year period before they launched their lawsuit.

According to estimates by the authority and the Public Doctors' Association, between 500 and 800 public doctors are on call on any one day. They have a one in 10 chance of being called upon to work. Doctors on call must be reachable, may not consume alcohol and must be able to get to hospital within half an hour.

According to some hospital executives, some specialities have doctors at five levels of seniority on call. Junior doctors take the first call and can seek help from senior doctors. Consultants and the chief of service might be called out on the third and fourth call as needed. Under the reform plan, these layers will be trimmed to three for most specialities. Hospitals will also consider sharing doctors on call.

One hospital executive feared the ruling would put extra pressure on frontline staff. The authority has introduced schemes aimed at reducing the working week of doctors to 65 hours or less.

'Under the ruling, we have to compensate for all off-site calls. If we compensate doctors by paying them and count the hours they spend on off-site calls, their working hours could easily exceed 65 per week. If we compensate them by giving them extra days off, we will need more doctors,' the executive said.

Public Doctors Association president Dr Ho Pak-leung said the fact the ruling made clear there was no ceiling on the amount of hours worked by doctors was demoralising.

'We are disappointed that our long battle for better work conditions has yielded no fruit. Doctors are the only workers in the public health-care sector who are not protected beyond a 44-hour week.'

Ho also said that cutting the number of doctors on call would compromise patient care. 'There will be fewer doctors answering emergencies. Also, some doctors may have to work in different specialities, which is not good for patient care.'

Tim Pang Hung-cheong, spokesman for the Patients' Rights Association, was concerned that there would be no senior doctors on call to handle emergencies.