Tobacco sales have slumped by 10 per cent following a tax increase that led many smokers either to quit or cut down.

"The number of cigarettes released for sale per adult is now at its lowest in 90 years," said the chairman of the End Smoking Trust, Dr Murray Laugesen, a public health specialist.

"This result is in line with the 15 per cent decrease in supermarket sales we reported after the 12 per cent May increase in tobacco excise 12 months ago," he said.

A spokeswoman for Associate Health Minister Tariana Turia said yesterday that the minister, who was to return from overseas last night, would be delighted by the decrease, although she had not yet seen the figures.

Around 20 per cent of adults smoke. Based on Government tobacco tax data, Dr Laugesen calculated that the equivalent of 969 cigarettes per adult were sold in 2010, down from 1080 the previous year.

The figures include all adults, not just smokers, and loose tobacco as well as factory-made cigarettes.

He said it was impossible to know from the data what the contributions of quitting and cutting down were to the overall sales reduction.

However, figures released earlier by the government's Quit Group suggest the number of smokers giving up the habit has increased as a result of last May's tax hike - which was followed by another in January, ahead of the third and last of the trio of tax rises next January.

The number of people who called the Quitline last May was nearly double the number recorded in May 2009. A check later last year found that after six months, 17.2 per cent of smokers who had called the Quitline in May were still not smoking. The organisation said this was "comparable to Quitline's standard quit success measure of 20.9 per cent".

"The key outcome is that there were 59 per cent more people successfully quit at six months than there would have been without the tax increase ..."