The debate over selling alcohol to minors shows no sign of diminishing after prosecutions of Asda and Bargain Booze staff delivered different verdicts.

Two Bargain Booze workers in Liverpool - both experienced retailers and also mothers - have overturned a Trading Standards prosecution by arguing that the underage test purchaser was made to look much older than she was.

Matthew Hughes, joint MD of off-licence chain Bargain Booze, said: "We're pleased they've been exonerated. It's nice that there are cases like this where common sense prevails."

Doug McQueen, the owner of the two franchised outlets that were involved, said: "Liverpool Trading Standards is criminalising housewives."

The stores do not sell alcohol to anyone younger than 21. But McQueen insisted the 15-year old girl in the sting was made to look substantially older. The judge hearing the case agreed after he saw CCTV images. He found the staff not guilty.

However, Rahul Verma, a former Asda sales assistant at a store in Beckton, London, lost her appeal against a conviction for selling alcopops to a 15-year-old test purchaser last year.

The incident prompted Asda to improve staff training and help found the Retail Alcohol Standards Group, which launched the industry-wide scheme encouraging sale of alcohol only to customers who looked older than 21.

The cases follow the submission of a proposed new test-purchasing code of conduct to the Home Office by Lacors, the licensing regulator. It is understood to recommend that test purchasers questioned by retailers should not lie about their age. An announcement is expected on the draft document this month.