A prominent Chinese-born academic has lost an appeal against Singapore's decision to expel him for allegedly being an "agent of influence" for a foreign government, the interior ministry said Wednesday.
Huang Jing, a US citizen who worked at leading postgraduate school the Lee Kuan Yew School of Public Policy, and his wife were stripped of their Singapore permanent residency status on August 4. 
Authorities accused him of working as "an agent of influence of a foreign country", and trying to use his prominent position to influence Singapore's foreign policy. 
His wife was accused of being aware of his activities.
They did not say which government he was accused of working for but the scholar has written extensively on China and regularly contributed to state-run media.
Huang and his wife appealed the government's move but the Ministry of Home Affairs said Wednesday it had rejected their challenge.
The pair "will have to leave Singapore within a stipulated grace period," a ministry statement said, adding both will be permanently banned from coming back to the city-state. 
It did not say how long the grace period was.
After news broke of the Singapore government's decision to revoke his permanent residency status, Huang told Hong Kong's South China Morning Post the allegations against him were "nonsense".
Huang's case comes at a time Singapore and China's historically warm ties are being tested.
There were tensions earlier this year when the southern Chinese city of Hong Kong seized nine Singapore armoured troop carriers as they returned to the city-state after conducting military exercises in Taiwan.
Beijing considers self-ruling Taiwan a renegade province awaiting reunification.