Law enforcement officers can't be expected to stamp out smoking in prohibited areas on their own and the Hong Kong public must do their part by "staring" at those who light up where they shouldn't, the health secretary said on Friday.

Expanding no-smoking zones and banning "smoking while walking" are among the ideas included in an ongoing public consultation exercise on how the city can become smoke-free.

At a Legislative Council panel meeting, election committee lawmaker Chan Wing-kwong suggested using security camera footage or videos captured by the public as evidence against people smoking in prohibited areas.

Health chief Lo Chung-mau agreed that the public have a role to play, saying it wouldn't be easy for law enforcement officers to arrive in time to catch smokers.

"Like queuing up at a bus station, for example, no one would actually regulate the behaviour, enforce proper queues by calling the police. We need to have a culture in society that people are willing to comply with the law," Lo said.

"If someone smokes or takes out a cigarette in the public venue, everyone should stare at that person. All the people at the venue should stare at that person."

Other lawmakers, including the Liberal Party's Peter Shiu, said they are worried that the government's proposed measures to cut the number of smokers are too stringent.

Shiu, who represents the wholesale and retail sector, said he doesn't think Hong Kong should follow New Zealand in banning anyone born after a certain date from buying cigarettes.

"What about when a child turns 28 years old or 38 years old? How can you restrict the liberty of people in Hong Kong, whereas other people in other parts of the world can actually smoke?" he questioned.

DAB legislator Leung Hei said he is concerned that strict tobacco control would affect the city's image.

Lo responded by saying visitors will be informed of Hong Kong's smoking measures before they arrive.

"We have to move towards a vibrant, healthy, and tobacco-free Hong Kong. That is a healthy image of Hong Kong," he said.