Management consultant Jackie Slater thought she was completing a normal shopping trip to Morrisons until the checkout assistant demanded to see her ID before scanning two bottles of wine.

"I told her I was really flattered, but I was the wrong side of 50," she said. But the assistant pointed to her 17-year-old daughter, Emily, and her 18-year-old niece, Annice, who were standing at the end of the checkout chatting.

"She asked: 'Are they with you?' I said they'd come to help me carry the bags back to the car. The assistant said: 'You could be buying the wine for them. It's the policy – I have to see everyone's ID to make sure they are all over 18'."

In vain, Mrs Slater insisted that the wine was for herself and her husband, Peter. But the assistant and then the store manager refused to budge.

Nor was their decision deemed an over-enthusiastic interpretation of company rules. Morrisons' head office last week backed the store – a move that suggests new guidelines, introduced to limit access to alcohol among youngsters, could soon cause chaos if other shops follow Morrisons' lead.

"Under current licensing laws, stores are unable to sell an alcoholic product to a customer they believe could be buying for a minor or for someone who is unable to prove their age," said a spokesman for Morrisons, citing the Think 25 scheme that has been put in place by major retailers to prevent the sale of prohibited items to under-age shoppers.

Morrisons does not contest Mrs Slater's version of events. The assistant even agreed that she would have sold the wine to a mother who had younger children with her because "no one would buy wine for a 12-year-old". However she still refused to scan the wine without seeing Mrs Slater's daughter's ID – which she did not have with her.

"I was embarrassed, there was a huge queue building up and my daughter found it all excruciating," said Mrs Slater, who describes the incident as "the silliest bit of jobsworth nonsense" she had ever come across.

"It comes to something when a mother can't take her daughter shopping without being made to feel like a criminal."

Last week Asda had to apologise to Gill Power who was told that her 14-year-old son was not allowed to help her carry shopping bags containing a bottle of wine. Mrs Power was told by the cashier: "Sorry he isn't allowed to take it because he is under age."

Asda later said its staff had been "overly cautious".

Morrisons is unrepentant about its Leeds store's decision. "We take our responsibility with regard to selling alcohol very seriously." said the spokesman. "The rules are in place to protect our customers and their families, as well as local communities who, in the majority of cases, appreciate our vigilance in the sale of age-restricted products."

Mrs Slater's MP, Greg Mulholland, a health spokesman for the Liberal Democrats, said: "Whoever thinks this policy will do anything to stop antisocial drinking by kids is in cloud-cuckoo-land.

"This is simply absurd and Morrisons should be ashamed of themselves.

"We need a more mature and sensible approach to alcohol in general – and refusing a mum a bottle of wine with the weekly shop because she has her 17-year-old daughter with her is ridiculous. Morrisons need to think again and this time do so with just a little common sense."