Four Vale off-licences have been caught serving alcohol to under-18s as part of an operation by police.
It involved two people under the age of 18 visiting six premises in the early hours in the evening.
Four failed the test by serving alcohol to the youngsters.
Police would not disclose the off-licences that had failed the test.
The operation targeted shops where intelligence suggested they were breaching their licensing conditions.
Premises which failed were served with fixed penalty notices and warning letters, informing them of further action if they failed to comply with licensing conditions.
Licensing officer Trevor Hooper, said: “The operation was carried out as part of our ongoing initiative to help keep people safe as they enjoy the night-time economies across Aylesbury Vale.
“We are extremely disappointed with the breaches at the tested premises during this operation.
“All licensed premises should operate with the four objectives in mind.
“One of these is the protection of children from harm - they clearly failed to support this objective.
“We will work in partnership with Aylesbury Vale District Council to continuously visit premises, and inform licensees of the licensing conditions that must be adhered to ensure the premises are managed effectively.”
Peter Seal, licensing manager for the district council added: “We will continue to carry out this enforcement activity to highlight where improvements need to be made and to work with licensees to achieve this.
“It is important to highlight that premises that are identified as inadequate and breach their conditions are open to review of their license and can end up appearing in court.”