A doctors' lobby group has warned that a tobacco tax that comes into effect on Sunday , will hit low-income people and those with mental illnesses particularly hard.

The 12.5 per cent tobacco tax hike is expected to raise $5.3 billion over four years, with the average smoker to pay an extra $10 a week.

Australian Association of Smoking Cessation Professionals vice-president Colin Mendelsohn said the tax hike, which comes into effect four weeks before Christmas, would most affect people in lower socio-economic groups, where smoking is most prevalent.

"I really think that it's exploiting smokers – who are drug addicts – who want to quit but can't," Dr Mendelsohn said.

“This is of special concern for disadvantaged groups such as people with mental illness, those from lower socio-economic groups and indigenous populations. These smokers have lower disposable income and lower quit rates, and those who are unable to quit are likely to be doubly disadvantaged by the price rise.”

It was a sentiment echoed by Treasurer Joe Hockey in opposition in August, when then prime minister Kevin Rudd announced the tax hike.

"It is going to increase the cost of living for smokers, but smokers could be pensioners, low-income people, it could be smokes and beers might be the thing that is important to them," Mr Hockey said.

"I want to know what the impact is on lower income people of just increasing their cost of living."

A Health Department spokesman said the government and the states wanted to reduce the national adult daily smoking rate to 10 per cent by 2018.

He said the government supported a range of quit programs, including some targeted at disadvantaged people, such as listing nicotine replacement therapies on the PBS, and had spent more than $135 million on quit smoking social marketing campaigns.

While the Association of Smoking Cessation Professionals acknowledges the tax will lower smoking rates, a move it supports, it says the government should offer more help to smokers struggling to quit.

Dr Mendelsohn said just one in 20 smokers managed to successfully quit smoking cold turkey, compared with a 25-30 per cent success rate for those who combined counselling and medication.

"Higher prices are good, but what we need to provide with that is professional support, and with that more of them will be able to quit."

The government had already hit smokers with increased excise duty of an average 4.7 per cent in the May budget, raising the effect of the additional tax hike of 12.5 per cent a year for the next four years. The two series of tax hikes combined will almost double the cigarette tax from 36¢ a cigarette this year to 69¢ by 2017.

Announcing the tax hike in August, Mr Rudd said: "Around 30 per cent of cancer is caused by tobacco consumption and it's estimated this will kill 15,000 Australians each year."