The overwhelming majority of parents want teenagers to face random drug-testing at school because they fear their children have access to illegal substances.
Two-thirds of parents back random testing amid concern that secondaries are not doing enough to tackle youth drug culture.
Four in five worry that their child has access to drugs at school, according to a survey by polling company IFF research. Concern about drugs was greatest in Scotland where almost all parents (95 per cent) admitted to being worried about the situation.
A Channel 4 documentary, This Teen Life, broadcast last September, claimed that more than half of 14-19s had encountered drugs or alcohol for sale in school.
Nearly half of parents believe that testing would be the most effective way of reducing drug abuse among teenagers, compared with fewer than one in five who favoured information campaigns and one in nine who supported a greater police presence near schools with problems.
Heavier penalties for teenagers caught with drugs and the appointment of a new Government "tsar" attracted even less support.
The findings are the result of 640 face-to-face interviews with parents and guardians of teenagers in the UK carried out for drug-test supplier Euromed, whose clients include NHS Trusts and the UK Prison Service. John Fritz, Euromed's managing director, said: "Random testing has proven a successful methodology for tackling drug misuse."