The 51-year-old chairman of the Singapore Democratic Party (SDP), Mr Jeffrey George, has been arrested for a drug offence, The Straits Times understands.
SDP secretary-general Chee Soon Juan told the paper last night that the news of Mr George's arrest came as a shock.
"I have known Jeff for many years and all this time he has discharged his duties as an SDP member and leader with professionalism. He is respected and well liked by his party colleagues," he said.
The Central Narcotics Bureau, when asked if Mr George had been arrested, said through a spokesman: "A 51-year-old man has been arrested for drug-related offences. Investigations are ongoing."
A shipping engineer, Mr George was elected chairman of the opposition party in October 2013. He was an election agent for Dr Chee and SDP vice-chairman John Tan in September's general election.
Dr Chee added last night: "At this time, the family members need support as they go through a difficult period. They should be left alone to sort things out."