A TOP Chinese University doctor has warned that Hong Kong's public health system will suffer badly if the Government continues to pay public health doctors less than those in hospital medicine. Professor Owen Lloyd, former head of community medicine at the Chinese University who resigned in protest over the policy, sounded the warning only hours before he flew out of Hong Kong last week. He said he was seriously worried about the future of public health in Hong Kong, adding that the pay policy would make it difficult to attract top medical graduates to the discipline. ''If you go into public health and preventative medicine, you get less pay [than hospital doctors],'' he said. The difference amounted to as much as 40 per cent less salary for public health doctors on local terms, he said. The Government agreed to pay university doctors the same as their counterparts in the Hospital Authority after they threatened industrial action last year, but this applied only to those involved in clinical work such as surgery. Professor Lloyd said Hong Kong people would suffer in the long-run. ''The way to build the health of a nation is not to build expensive hospitals; it's to get in at the grassroots level with health prevention and promotion,'' he said. Professor Lloyd said the Chinese University's public health doctors had begun drawing up health maps of Hong Kong which showed a five-fold to six-fold difference in the incidence of diseases, such as certain cancers, in different parts of the territory. ''These are preventable diseases and we should be preventing them,'' he said. ''But in downgrading our community and family medicine departments, Hong Kong is just shooting itself in the foot,'' he said. Professor Lloyd has gone to the University of the United Arab Emirates.