Fewer than one in five adults in England now smokes, the smallest fraction in three generations, the British Medical Journal (BMJ) has reported.
In a letter, health researchers Jamie Brown and Robert West of University College London reported on a seven-year-old program to monitor smoking prevalence in England.
It samples 1,800 people aged over 16 who are randomly chosen each month.
In 2013, 19.3 per cent of those questioned said they smoked.
"For the first time in probably 80 years, smoking prevalence in England has fallen below 20 per cent," the letter said.
Smoking in England was rare at the start of the 20th century and reached a peak in the early 1960s, when more than 70 per cent of men and 40 per cent of women smoked.
Brown and West said smashing the 20 per cent mark could be an important moment in rolling back tobacco.
The decline in smoking prevalence in England began in the 1970s, they said, with an annual fall of 0.6 percentage points a year on average. The retreat in 2013 was slightly higher at 0.8 per cent.
"Much is still to be done," the pair wrote. "However, we hope that breaking the 20-per cent barrier will motivate smoking cessation efforts across the country."
