The stores include branches of Tesco, Asda, Sainsbury's and Marks and Spencer, police said.

The stores' managers in Nottingham have been given a final warning by police, who have vowed to crack down on alcohol misuse in the run up to Christmas.

The warning was issued after an undercover police sting last weekend.

'Disgraceful' results

Staff at 60% of the stores tested failed to stop youngsters under 16 from buying alcohol.

Nottingham is one of just five cities to receive a �40,000 Home Office grant to target booze-related violence on the streets.

Retailers have a legal and moral duty to prevent young people from buying alcohol Superintendent David Walker, Nottinghamshire police

At a meeting with senior officers, managers were told that the results of the survey were a "disgrace" and were warned that another offence could lead to a revocation of their drinks licence.

Superintendent David Walker, head of operational policing in the city centre, told them: "You have to correct your procedures and put your house in order, because if you continue to contravene, there will be implications for your business.

"Retailers have a legal and moral duty to prevent young people from buying alcohol and I would urge you to reinforce that message to all of your staff."

Soon after the blunders were revealed, all the stores involved vowed to keep a closer eye on staff to ensure there were no further issues.

Other stores caught selling alcohol to underage customers included Jacksons, Spar, Budgen's, Co-op and Iceland.

Many major retailers issued statements detailing their strict identification policy and commitment to clamping down on alcohol misuse.

Inspector Paul Winter, who led last week's undercover operation, said he is pleased with their response.