They are being issued amid concern that one in five schools have no explicit policy on how to respond if a pupil is found in possession of illegal substances.

The new guidelines come a day after the School Standards Minister, Estelle Morris, caused controversy by calling on schools to think twice before expelling children found to be carrying drugs.

The guidelines make a clear distinction between the possession of drugs and trafficking in drugs.

While they say that trafficking should always result in a child's exclusion, either fixed-term or permanent, possession is a different matter.

Charles Clarke: "Pupils must be made aware of the risks of drug abuse before they are likely to be drawn into experimentation"

Pupils found in possession of drugs should not automatically be excluded, the guidelines say. The school's response should meet the best interests of both the child found with drugs and the rest of the school.

Simply informing the police - a course of action which must always be followed when drugs are found in school - may be sufficient punishment for a child who has never been in trouble before.

Alongside punishment, teachers are asked bear in mind the welfare of the individual and how best to reinforce the message that taking drugs is wrong.

The guidelines also stress the importance of drug education as part of a wider personal, social and health education programme that begins in primary school and is continued in secondary school.

The new guidelines were announced by the Schools Minister, Charles Clarke, who also launched a drug education website for teachers at Forest Gate Community School in east London.

Set up by the Institute for the Study of Drug Dependence and partly funded by the Department for Education and Employment, the website is designed to give teachers up to the minute information about drug education.

Mr Clarke said: "Teachers are at the forefront in giving young people the information and skills to make healthy responsible choices and resist drugs.

"Most schools have taken the issue of drugs seriously, developing policies and delivering good quality drug education.

"But we want to make sure the coverage is more systematic and that no school regards drugs as an issue to be swept under the carpet."