Leicester City Police sent 15 and 16-year-old volunteers into the Tesco Express on Ryder Road in March and November last year.
Both times the store was caught out, and at a licence review at Leicester Town Hall on February 7 it was stripped of its licence for a month.
Qwik News on Beaumont Leys and The Off-Licence, in Knighton Fields Road were also caught. They had conditions placed on their licences including installation of CCTV, staff training, the compiling of a refusal log and the labelling of all alcohol containers with the shop name.
PC Jon Webb, from the city licensing team, said: “There really is no excuse – it’s quite simple to ask someone who does not look old enough for valid proof of age and if they don’t have it, refuse them. Challenge 21 and 25 are there to assist sellers and to inform customers they will be challenged, yet we see same premises failing the test.
“Hopefully by having these conditions placed on their licence, and by Tesco having a one month suspension, the three shops will get their premises in order and will move forward with a positive attitude and responsible approach to selling alcohol.”