Privacy Commissioner for Personal Data Roderick Woo Bun has cast doubt over whether students - or their parents - have the legal capacity to give consent to a voluntary drug test and says new laws might be needed before any scheme can go ahead.

His concerns were outlined in a letter sent to Secretary for Education Michael Suen Ming-yeung yesterday.

Woo said: "While it is doubtful whether all students have the requisite capacity to give genuine consent, the Personal Data (Privacy) Ordinance does not give parents or guardians the authority to give consent on behalf of a minor." He added that the situation has to be resolved by new legislation.

Woo's intervention came as the debate over drug testing in schools threatened to descend into farce when a top education official said he would take a test and the Catholic Church suggested government officials, school staff and celebrities follow suit.

Undersecretary for Education Kenneth Chen Wei-on said he would take a voluntary drug test when the scheme starts in Tai Po schools later this year. Chen told a radio station caller: "If students think this [me taking a test] is important to them, I will support it."

Asked if Chief Executive Donald Tsang Yam-kuen would support such a move, Chen said it is a new idea and more views should be gathered.

His offer came as the Catholic diocese's social communications office director Dominic Yung Yuk-yu suggested school principals, teachers, celebrities and government officials take drug tests with students.

A Secondary Seven student, identified as Yoyo, doubted the effectiveness of the church's call.

"If people are unwilling to take the test they will still refuse to do so no matter who takes part," she said. Chen said the pilot scheme would be launched at 23 schools in Tai Po in December and pledged no more delays.

Action Committee Against Narcotics chairman Daniel Shek Tan- lei said more discussion is needed.

Education Convergence vice chairman Ho Hon-kuen accused Catholic Church spokesman Yung of setting a bad example to students.

"It's a little too dramatic trying to involve teachers, janitors and even celebrities," Ho said.

"The drug test is something serious. It [Yung's proposal] seems like holding a gala at schools and it will not serve as a positive demonstration to students."

He said that it would also mean additional costs and added the controversy has arisen because the government is pushing the scheme through too quickly.

Social welfare lawmaker Cheung Kwok-che described Yung's suggestion as "unlikely to be feasible" because it involves too many people.

"If 20,000 students agree to take the test, does that mean that 20,000 teachers and celebrities will have to do the same? These questions remain unanswered," he said.

Cheung also said if tests identify a number of drug abusers there may not be enough social workers to cope.