Pub and off-licence workers who sold booze to underage customers have been ordered to attend police training sessions.
Nine members of staff at pubs and off-licences, primarily in Morley and Middleton, were caught selling alcohol to buyers aged 15 and 16 in a police operation over Christmas.
Forty-seven premises were tested in total.
Those that failed the test were given community resolutions, which include conditions that they attend a police station, accompanied by their manager or the licensee, to be reminded of their responsibilities.
Licensing officer Sgt Dave Shaw said: “The Christmas period is a time when we have an increased focus on licensing issues that can impact on crime and anti-social behaviour.
“The results of this latest test purchase operation show a failure rate just short of a 20 per cent. We will be stepping up our test purchase operations throughout 2015 at pubs and off-licences across the Leeds district to ensure that children are protected.”