The ban on the sale of 10- and 15packs, effective since 31 May, was introduced to price youngsters out of the market. But it has left some moderate adult smokers unable to monitor their consumption.

"I predict that our sales will go up. A lot of adults used to only smoke 10 a day.

It's about portion control. But now many are smoking more because they have no choice but to buy 20, " said Deirdre Healy, corporate affairs manager for John Player & Sons.

It was too early to say whether under-18s were smoking less as a result of the price hike to 7, but it would be naive to think that many would not continue smoking regardless, Healy added. "A recent study has shown that children in Ireland have a lot of spending power, " she continued.

The Office of Tobacco Control (OTC) said 10 packs were known as "kiddie packs". A recent OTC report found that, before the ban, 76% of smokers typically bought 10 packs and 77% of 25+ smokers bought 20 packs.

"Internationally, 10 packs are called 'kiddie packs' . . . starter kits for nicotine addiction, as they are priced and targeted at the extremely price-conscious youth. By only having 20 packs available, some young people will be deterred from starting at all, others will delay starting, others will experiment less with tobacco products and not go on to be addicted and others will quit smoking, " said OTC spokeswoman Kathleen Quinlan.