Changes to the local law mean it will be an offence to smoke in Perth's malls. Picture: Sharon Smith/The West Australian

City of Perth will become the first council in WA to ban smoking in major pedestrian areas when its malls go smoke-free from Sunday.

Changes to the local law mean it will be an offence to smoke in Perth's Hay St Mall, Murray St Mall and Forrest Place.

Offenders in the first six months of the awareness campaign will be cautioned, and fines will be issued from June 1 next year.

Healthway chair Rosanna Capolingua said on Thursday nine in 10 people in WA were non-smokers and it was important to show young people that being a non-smoker was a community standard.

"We're talking about hundreds of thousands of city workers and visitors per week who will no longer be exposed to harmful second hand smoke in these areas," she said.

"Smokers too will benefit from this move, and most agree it's a good idea because they want encouragement to quit.

"We've found by reducing the number of places people can smoke, the less they do smoke."

Healthway ambassadors will be in the malls during peak periods from Monday and at major city events over summer to inform the public of the local law changes.

Lord Mayor Lisa Scaffidi said there was a lot of public support for the initiative.

"This is something Perth people told us they wanted and if the social media chatter is anything to go by, they're more than ready to embrace this change," she said.