Roll-your-own smokes could be even more harmful than factory-made cigarettes because people suck them harder and more efficiently, Christchurch research indicates.

The researchers are calling for the Government to act on their findings by applying a higher tax and specific warnings on roll-your-own tobacco.

In the first comparison between the two types of smoking using people rather than smoking machines, the study suggests rollies are "apparently no less and possibly more dangerous" than factory-made cigarettes.

Public health specialist Dr Murray Laugesen and his co-researchers found roll-your-own smokers inhaled 28 per cent more smoke per filtered cigarette, even though the rollies contained less tobacco than the factory-mades.

And both types boosted the level of carbon monoxide, measured in exhaled breath, by the same amount.

"Whereas a smoker of factory-mades lets a lot of the smoke go up in the air, these roll-your-own smokers suck like crazy and don't let so much be wasted," Dr Laugesen said yesterday. "They're getting more value out of the tobacco - and more harm."

The study, using cigarette holders containing flow meters, compared 26 people who usually smoke rollies with 22 who usually smoke factory-mades.

In their paper, the researchers said rollies accounted for nearly a third of tobacco used in New Zealand.

The country's comparatively high tobacco excise tax - levied by tobacco content, not per cigarette - had encouraged smokers to hand-roll thin cigarettes and pay less tax.

"Thus excise increases have perversely encouraged cheaper smoking rather than quitting."

Overseas research has shown roll-your-own smokers are twice as likely as smokers of factory-mades to believe rollies are less risky. Norwegian research shows they also have twice the lung-cancer risk. Although rollies contain less tobacco, they contain no fewer additives and their smoke contains much more tar.

Associate Health Minister Tariana Turia wants more tax on roll-your-own tobacco, but a spokesman for the Finance Minister said the Government was not considering it.

A study that compared smoking of roll-your-own and factory-made cigarettes showed rollie smokers:
* Inhaled 28 per cent more smoke per cigarette.
* Took 25 per cent more puffs.
* Puffed for six seconds longer per cigarette.
* Increased their carbon monoxide level by the same amount.