The Department of Home Affairs says in future it will carry out its own surveys of drug use among Manx youngsters.
In recent years data's been collected by the European School Project on Alcohol and other Drugs, or ESPAD.
The figures have been used in a UN survey which suggests the Island has the world's highest use of cocaine per-head-of-population.
It's been branded misleading for applying results from a survey of 15-17 year olds, across the whole population.
Now, ESPAD's survey methods have been questioned by Home Affairs bosses.
Director of Administration Julian Lalor Smith says flaws were found when the questionnaire was analysed:
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