The idea is being reviewed by the Lord Advocate. It would bring Scottish law in line with that in England and Wales and is strongly backed by the anti-smoking lobby, including the Parliament's cross-party group on tobacco control, ASH Scotland, the cancer charities and local authority trading standards officers.
Although their evidence cannot be used in court, child "test purchasers" have already been tried out in some Scottish local authorities. Children aged 10-14 have been used, accompanied by trading standards officers, and acting according to strict Crown Office guidelines.
But the Scottish Parent Teacher Council says in its response to the Lord Advocate's review that it has "grave reservations" both about such children acting as test-purchasers, and about any requirement for them to act as prosecution witnesses.
Fears were expressed over their safety - and possible reprisals from shopkeepers. "The bottom line for all the parents we consulted was that no one could contemplate allowing their children to be used - so they did not think it reasonable to expect others to do so," the SPTC states.
Judith Gillespie, the council's development manager, asked whether that "even if you did stop under-age purchase, would you stop under-age consumption? You just have to give children realistic alternatives so they do not want to indulge in what is a form of escapism."
Children in Scotland's policy committee, has "ethical considerations" to offer, particularly if the children of trading standards officers were to be targeted.
Douglas Hamilton, its policy officer, asks: "How can we be sure such children are fully informed and freely consent to being used as test purchasers?
"And could it be the case that trading standards officers have not sufficiently prioritised other methods, such as the surveillance of shops?" In England, the prospect of using the evidence of child test purchasers in court has led to a dramatic rise in the number of shop keepers being successfully prosecuted - even without the test purchasers themselves having to appear in court.
But Colin Boyd, the Lord Advocate, said in a statement that "it would be difficult, if not impossible, to ensure that the child does not have to give evidence in court".