But Richard Peto, professor of medical statistics at the University of Oxford, warned that smoking remains the major distinguishing factor in the mortality of people in different social classes.
"The poor, the uneducated, those in low social classes, smoke more," he said. "The difference in tobacco deaths between rich and poor people accounts for most of the inequalities in their health."
That gap between rich and poor has been widening for decades, he said - except in the Depression when only the rich could afford to smoke enough to kill themselves.
The drop in mortality means that Britain has moved from having the world's worst death rate due to smoking, to having the best, said Professor Peto.
In 1970, Britons smoked 150 billion cigarettes, and 80,000 people died of smoking-related illnesses such as lung cancer and heart disease. Of men aged between 35 and 69, 19 per cent died prematurely. For the whole age group, 42 per cent died from causes including accidents and illnesses.
But by 1995, annual cigarette sales had fallen to 80 billion, and smoking- related deaths to 40,000.
Among middle-aged men, smoking killed just 9 per cent, while 28 per cent of the whole age group died. That means that two-thirds of the fall in mortality for middle-aged men was the result of the drop in smoking; but it also means that a third of deaths in middle age are caused by tobacco.
Many of the victims are people on lower incomes. Professor Peto said: "Professionals have one-fifth the lung cancer rate of the unemployed. The unemployed smoke more."
The British improvement in mortality is better than that of the United States. Even though the US is generally thought of as virulently anti- smoking, 12 per cent of middle-aged men there die from smoking-related illness, and 6 per cent of women.
But Professor Peto emphasised that for smokers "it's still a 50:50 chance that if you smoke, it'll kill you. It's not even dicing with death - at least then you would have a one in six chance of surviving. The fact is that the odds if you smoke aren't even as good as playing Russian Roulette."
The task is to persuade more smokers to give up the habit, Professor Peto said.
His research suggests that people who quit smoking by the age of 35 revert to the same health risk as somebody who has never smoked.
Jean King of the Cancer Research Campaign said: "Part of the problem is that you cannot get treatment to give up smoking such as nicotine patches on the National Health Service. It could be done for people on low income or benefits, even if it would be too expensive to pay for everyone who's smoking."Reuse content