More than 400,000 people in England have given up smoking as a result of the ban on lighting up in public places introduced in July, according to a study published on Monday.
Researchers say 40,000 deaths will be prevented over the next decade as a result of the ban.
The Smoking Toolkit Study involved interviews with more than 32,000 smokers and ex-smokers over the nine months before the ban and the nine months afterwards.
Smoking was made an offence in all enclosed public spaces in England, including pubs and restaurants, on July 1, 2007, forcing smokers to take their cigarettes outside.
In the nine months preceding the ban, there was a 1.6 percent fall in the prevalence of smoking in England, but in the nine months after its implementation, the fall was 5.5 percent which researchers said equates to 400,000 people.
Despite some opposition to the tough legislation, compliance has been almost total.
Another study to be published this week, by the Department of Health, will show that a total of 234,060 people have stopped smoking with the help of a special service offered by the National Health Service since the ban came in.
Around 22 percent of the adult population still smokes in Britain.
Professor Robert West, Cancer Research UK's director of tobacco studies, who oversaw the study with funding from drug companies, said: "These figures show the largest fall in the number of smokers on record.
"The effect has been as large in all social groups, poor as well as rich smokers.
"I never expected such a dramatic impact and of course there are no guarantees that smoking rates will not climb back up again," he said.
"But if the Department of Health can keep up the momentum this has created, there is a realistic prospect of achieving a target of less than 15 percent of the population smoking within the next 10 years."
The health charity Action on Smoking and Health (Ash) welcomed the findings but called for extended action from the government to prevent children being affected by tobacco company marketing.