ZHUHAI should sue Hong Kong if it goes ahead with the multi-billion-dollar sewage disposal scheme without Beijing's approval, a mainland legal expert has said. The proposal came at an academic conference in Panyu, Guangdong, last week, with mainland Joint Liaison Group (JLG) experts and Hong Kong officials in attendance. Guangzhou academic Professor Wang Jinsan, who was at the conference and supported the proposal, revealed the idea was raised by a legal expert. Stage two of the scheme proposed by Hong Kong, which is currently on the JLG negotiating table, involves the use of outfall pipe to discharge sewage into waters that fall under the jurisdiction of the Special Economic Zone of Zhuhai. China has already voiced strong objections to the plan, but last week's conference was the first time that the prospect of taking legal action over it had been raised. The mainland legal expert told the conference that discharging sewage into neighbouring areas without consent breached a United Nations treaty on protecting the oceanic environment, to which Britain was a signatory. He said the Zhuhai Government should take the territory to the World Court if Hong Kong insisted on going ahead with the scheme. 'If they discharge sewage into Zhuhai, they will break the international treaty by seriously damaging our environment; Zhuhai could definitely sue Hong Kong,' Professor Wang said. A government spokesman yesterday denied receiving any threat of legal action.