Calls for a formal investigation are growing after Executive Councillor Franklin Lam Fan-keung was found to have made HK$10 million by selling two luxury flats just weeks before the government unveiled surprise measures to cool property prices. Although Lam has repeatedly said he was unaware of the upcoming decision, it does not dispel speculation that he benefited from his capacity as a cabinet member. Given the severity of the allegation, the public expect nothing short of a full investigation.

There is no evidence at this stage to prove the former property analyst at UBS investment bank had any insider knowledge. The properties in question were put on sale before Chief Executive Leung Chun-ying appointed Lam in July. Lam was said to be out of town when members were briefed on the stamp duty increase at a special Exco meeting shortly before a public announcement last Friday. The circumstances, as some suggest, do not constitute any conflict of interest.

It could also be pure coincidence that one of the buyers appears to be a mainlander, who would have been caught by the new measures had the transaction been made after the announcement. But it is common sense that cabinet members have access to officials' thinking during the early stages of policy formulation. If they are privy to the government's intention to roll out more anti-speculation measures, they stand to benefit by making an early deal even without knowing the specifics. We don't know whether this was the case. It is for the government to find out and give the public a full account.