Millennium Square and Anchor Square in Bristol will become Britain's first major public outdoor spaces to go smokefree when a voluntary pilot launches today.
The two city squares on Bristol's harbourside are popular with families.
The move to make them smokefree follows a major report last year by former health minister Lord Darzi which suggested that London and other UK cities should ban smoking in public spaces and parks.
Cities including New York, Toronto and Hong Kong have already banned smoking in key outdoor locations but Bristol is the UK's first to pilot smokefree zones. Words: PA
Millennium and Anchor Squares are home to the At-Bristol science museum, shops and restaurants, regularly host events and festivals and are well-used play spaces for children.
The pilot builds on the smokefree play parks project, which reduced smoking near playgrounds in the south west by 34% through bright, positive signs asking people not to light up.
Mother Kirsty Vass, 33, inspired the smokefree pilot in Bristol after being diagnosed with chronic obstructive pulmonary disease (COPD) a year ago when one of her lungs collapsed.
"My smoking illness has caused my whole world to come crashing down," Ms Vass, of Torbay, Devon, said.
"If young people see you smoking then they think its alight, but they don't understand what it can do to you, so making smoking less visible in public places can only be a good thing.
"I don't want other people to be like me because this isn't a life, it's a life sentence. If I can make people realise that this is what smoking does to you then please, please, please quit now because it's really not worth it, especially if you've got kids."
Extensive research in the squares ahead of the pilot found most people were in support of a voluntary ban.
Some 53% described it as a "good or very good idea" with 61% agreeing the area would be a better place for most people if it were smokefree.
Fiona Andrews is director of Smokefree South West, which initiated the voluntary pilot and expect it to police itself.
"This is an exciting initiative that we hope will have a lasting impact not only on Millennium Square and Anchor Square, but on the wider region," she said.
"These city centre squares are often full of children playing and this pilot will provide a smokefree environment for kids and their families to enjoy."
The smokefree zone will be promoted throughout the squares with signs that thank people for keeping Bristol smokefree, healthy and clean.
Councillor Daniella Radice, assistant mayor for Public Health at Bristol City Council, added: "In this year that Bristol is proud to be the European Green Capital, I am excited to see how this pilot can change people's habits and make Bristol an even more enjoyable place to live and to visit."
Campaigners from smokers' group Forest criticised the ban as an example of "creeping prohibition".
Simon Clark, director of Forest, said: "Smoking is banned in all enclosed public places. Now campaigners want to ban it outside. This is creeping prohibition.
"Extending public smoking bans to outdoor areas is illiberal and unwarranted.
"Smoking in the open air harms no-one apart, perhaps, from the consumer - and that's their choice.
"Tobacco is a legal product. Smokers contribute £10 billion a year in tobacco taxation alone. They must be allowed to light up somewhere without harassment."
Ryanair passenger arrested after causing mayhem on 'flight from hell'
Free breakfast is the best hotel perk for Brits