Hong Kong  - Hong Kong leader Donald Tsang Monday wrote to parents urging them to support a controversial programme to test 22,000 pupils for drugs.

Urine samples are to be taken from pupils in 23 schools and results shared between teachers, police and social workers in a move to tackle a growing tide of youth drug abuse.

However, the scheme has triggered criticism with academics and youth welfare groups saying it is draconian and unnecessary and complaining that it infringes civil liberties.

The government insists the trial scheme will go ahead and plans to implement it in December.

In his letter to parents, Tsang said: "Juvenile drug abuse has become serious in Hong Kong ... We need to mobilize the whole community to help our young people stay away from drugs."

Under the government scheme, parental consent is required to obtain urine samples from pupils aged under 18 while the consent of both parents and students is required for pupils aged 18 or above.

Serious drug cases in Hong Kong rose 2 per cent to 1,529 in the first half of 2009 year-on-year, according to police figures, and the number of cases in schools is rising.