NHS stop smoking services have helped almost 146,000 people quit long term, according to new research.
Data suggests that, over the last 10 years, around 145,783 people in England have quit smoking for at least 12 months.
A team led by Robert West, Cancer Research UK director of tobacco research at University College London, examined NHS services, which can include prescribing medication to help smokers quit as well as face-to-face counselling in groups or individually.
They found the services had "increased their reach and impact threefold" over the decade and were reaching poorer people with traditionally high rates of smoking.
Writing in the British Medical Journal (BMJ), they said around 35% of people who set a quit date had stopped smoking four weeks later.
And the number estimated to have quit in the long term (still not smoking 12 months later) was almost 22,000 in 2010/11 alone.
"Bearing in mind the difficulty in quitting experienced by smokers who typically attend stop smoking services, even a 35% four-week quit rate represents a substantial impact when applied to the nearly 800,000 quit dates set with the services in 2010/11 (700,000 smokers, or 8% of the nine million smokers in England," the authors wrote.
The team looked at smoking figures from 2001 to 2011 for the number of quit dates set (throughput).
Throughput rose from 227,335 in 2001/02 to 787,527 (8% of all smokers) in 2010/11.
While the percentage of four-week quitters declined slightly from 35% to 34%, this meant that, overall, the actual number of four-week quitters rose from 79,767 to 269,293.
The team concluded: "The English stop smoking services have had an increasing impact on national smoking cessation since 2001 by increasing throughput, with only a small decrease in the percentage of those treated who succeed.
"They have been successful in reaching economically disadvantaged smokers, with more than half of those treated being eligible for free prescriptions."
Until 2013, stop smoking services in England were provided through 151 primary care trusts. Since April this year, local authorities have held the budget. Each local area can run its service as it wants but is encouraged to follow national guidance.
Alison Cox, Cancer Research UK's head of tobacco policy, said: "Tobacco is a lethal product that kills half of all long-term smokers, so helping smokers to quit is an incredibly important job.
"With local authorities now in charge of this area of public health, these findings provide reassurance that stop smoking services are effective and provide value for money in reducing the deadly toll from tobacco.
"A close watch needs to be kept on the local provision of these services. Reduced support to smokers would be a very bad outcome of the NHS restructure as it would increase health inequalities, and could ultimately cost lives."
The researchers found that, while the overall picture is positive, there is a large variation in performance between local services, with some doing more than twice as well as others.
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Prof West said: "England's stop smoking services have led the world and saved lives more cost-effectively than just about any other area of the NHS - a real success story.
"However, there is clearly room for improvement and a need to bring the poorer performing services up to standard."
England's deputy chief medical officer, Professor David Walker, said: "Smoking is one of the biggest and most stubborn challenges in public health.
"The latest figures show that more people are getting the right support to help them quit long term. This is testament to the excellent work of health professionals across the country but we know more must be done.
"We want to drive down smoking rates even further - that's why we have published an ambitious plan for England, ended tobacco displays in large supermarkets and are running national campaigns to remind smokers of the harm."