Trading standards officers said they were appalled after 50 per cent of stores sold cigarettes to a 15-year-old schoolgirl.

A survey of eight newsagents, an off-licence and one post office in Oxford, showed two years after the legal age to buy cigarettes increased from 16 to 18-years-old, many shops were still not asking for identification.

Vanessa Walters, 15, from Bicester, did not try to conceal her age and admitted she was under 18 if challenged at the counter during our test last week.

The five failures were Quix, in Cowley Road, East Oxford; Littlemore Post Office, in Cowley Road, Littlemore; Martin’s, in Blackbird Leys; Globe Newsmarket, in Iffley Road; and Caspian News, in George Street.

Richard Webb, deputy head of Oxfordshire County Council trading standards, said: “It is appalling that half of the shops failed.

“That is an even higher failure rate than our operations.

“We are disappointed, but from our experience when we conduct interviews with shops that have failed, all their staff are correctly trained and every one knows the law. It is often just down to one member of staff who is not thinking at that time.

“We are glad this operation has been brought to our attention.”

The test-purchase operation was carried out on Friday during the school half-term holiday.

It is not illegal for anyone below 18-years-old to buy cigarettes, but it is against the law for the shop to sell them.

Trading standards tested 32 premises across Oxfordshire and nine failed during 2008/09.

Since April this year, trading standards have test-purchased 19 businesses. Three have failed.

Any shop which fails three times in a year risks losing its right to sell tobacco.

Amanda Sandford, of anti-smoking campaign group ASH, said: “It is shocking that retailers are still not upholding the law.

“What they are doing is aiding and abetting young people’s potential addiction – for life.”

Staff at the Co-operative Swift Shop, in Walton Street, Jericho; Martin’s, in Banbury Road, Summertown; Balfour News, in Cherwell Drive, Marston; Girdlestone Stores, in Headington; and Just Booze, in Wood Farm, all asked for ID and refused to sell to Miss Walters.

Kiren Turna, manager of Just Booze, said: “If I doubt anyone’s age and they have no ID I refuse to sell to them.”

During our test purchase operation in November two years ago all ten shops tested failed.

Quix, in Cowley Road, and Martin’s, in Blackbird Leys, which were two of the shops failed this year, sold cigarettes to a 16-year-old girl.