Bishop Richard Holloway sparked controversy in a Sunday newspaper interview to mark the launch of his latest book, Godless Morality, at the Edinburgh International Book Festival. Bishop Holloway said he had tried cannabis once, and that it was less harmful than alcohol and cigarettes, and backed calls for legalisation.

Speaking to The TES Scotland before his Edinburgh talk, he said drugs education should incorporate a message of moderation. “It is best located against a background of the western ethical tradition that life is dangerous. The wise approach is to handle things in it, such as drugs, with a certain temperate moderation.”

Bishop Holloway added: “I get the impression that probably the majority of youngsters are well aware of these dangers and they already make a balanced use of drugs as well as alcohol.”

Alistair Ramsay, executive director of Scotland Against Drugs, says drugs education has to evolve. “We need different messages for different groups. Pupils with experience of drugs have to be allowed to talk about it.”

But Mr Ramsay added: “Although teachers should not be simply saying no to youngsters, the whole question of the illegality of drugs has got to be in there.”

He said the huge gap in drug education was the failure to say “well done” to children who have not been taking any drugs.

Bishop Holloway acknowledged “the difficulties teachers have in talking intelligently about drugs to youngsters. As long as the drugs young people choose are criminal how can teachers be talking about their moderate use?”

He added: “Drug counsellors are finding this an increasingly difficult thing to do, yet they are still getting good information out.”

Contrasting education about alcohol and under-age sex, Bishop Holloway said:

“When kids are practising under-age sex, you know that while it is illegal you hope they are practising safe sex.

“Teachers have to live in the world as it is. It is a complex, rather hypocritical world where recreational drugs are concerned. The realistic ones will be saying to their pupils, this is exciting but dangerous stuff. If you are going to experiment with it, do it wisely. If you are going to use these substances, understand the implications - and the effects.”

Bishop Holloway suggested there was a place for drugs education within religious and moral education. “The basic subtext is moral education - how do we live wisely in a world that is filled with dangerous and seductive substances and experiences?”

His proposal was met with scorn by Ian Barr, director of the Scottish Consultative Council on the Curriculum. “If we included drugs education in religious and moral education, where would we stop? Traffic education or the state of the rain forest would also have to be included.”

Mr Barr added: “There are moral aspects in all parts of life. Drugs are one issue you need to have a positive attitude towards, not from a problem-centred approach but as a set of principles to be applied to treating the world with respect.”