Chief Executive John Lee urged people without proper training to refrain from mounting sting operations, after taxi drivers went undercover to try to tackle unlicensed ride-hailing services.

Cabbies raised eyebrows and caused controversy by travelling as Uber passengers before asking drivers to stop at locations the police had been called to.

But Lee warned there were risks for people taking matters into their own hands, and that they should refer the issue to law enforcement officers instead.

"These operations should be undertaken by law enforcement agencies. And the law enforcement agencies that take these undercover actions will have to abide by rules and regulations. The officers involved have been well-trained. They act within the framework of the law," he said.

"You need training to handle emergency situations. Without proper training and without adequate legal understanding, I advise people not to do it, because they may break the law."

The CE also noted the Transport and Logistics Bureau would report to lawmakers the results of a study on ride-hailing services in July.