A ban on the sale of cigarette 10-packs - introduced in the Republic of Ireland to discourage young people from taking up smoking - will backfire, a leading tobacco company has warned.

Experience abroad suggested cigarette sales would rise as a result of the ban rather than fall, according to John Player & Sons. "Many adults have been buying a 10-pack a day to manage their consumption," said corporate affairs manager Deirdre Healy. "If only 20s are available, the temptation will be to smoke more.

"When France introduced a ban on 10s last January, practically all volumes of 10s transferred into 20s. Based on this precedent, we expect a similar pattern to occur in Ireland and have allowed for extra stocks accordingly."

The situation would be exacerbated because of the high market share traditionally held by 10-packs in the Republic, she said. "Only 3% of the French cigarette market was in 10s, while in Ireland it was 33%."

The Irish Health Department's Office of Tobacco Control insisted the ban was still the most effective way of cutting the very young out of the market.

"Packs of 10 are a gateway to smoking," said a spokesman. "Some could argue that the difference between €3 for a 10-pack and €7 for 20 won't put off 17-year-olds, but it will deter the 12-year-olds."

John Player's comments will be noted this side of the Irish Sea. Last month the UK government said it was considering a ban on 10-packs as part of its own initiative to deter minors from smoking.