Underage children in Cumbria managed to buy cigarettes from pub vending machines in 13 out of 13 tested venues in a sting operation.
The pubs in Keswick, Carlisle and Barrow have been warned they must do more to stop underage sales or face prosecution.
The sting operation was carried out by Cumbria Trading Standards using a 14-year-old boy and a 15-year-old girl.
The trade will be irate that another round of sting operations is heading its way after the incessant underage drinking campaigns and the Christmas blitz on serving drunks.
But it is vital that pubs get their house in order to fend off calls from the British Medical Association to ban vending machines altogether.
"This exercise has shown an alarming lack of diligence on the part of landlords who are responsible for supervising the use of cigarette machines on their premises," said head of Cumbria Trading Standards Phil Ashcroft.
"Warnings have been issued to the thirteen pubs who failed this exercise and landlords across Cumbria can expect prosecution and the removal of cigarette vending machines if they turn a blind eye to children buying cigarettes in their pubs."