The advice is part of more government guidelines that will educate parents and children about the dangers of drinking. It is thought the guidelines will also contain a requirement for those selling alcohol to request ID from people who look under 21.Many pubs and off-licences already operate a voluntary ‘Challenge 21’ policy and some have upped this age to ‘Challenge 25’.The advice is expected to spark debate about how best to encourage sensible drinking. Questions have also been raised about the cheapness and availability of some alcohol but Donaldson said today's guidelines are more about practical advice for parents and children. Diageo welcomed the guidance. A statement from Diageo GB said: “Diageo shares the concerns of many people about underage drinking and welcomes the consultation on the new medical guidance outlined today by the Chief Medical Officer. "This is a mature response by the Government in trying to tackle a serious problem. Young people’s drinking behaviour cannot be taken in isolation and we are also pleased to see Government’s recognition of the role of parents and carers in promoting a responsible attitude towards alcohol. Adults need to be able to explain to their children what a unit of alcohol is, what alcohol does to the body and why it is important to drink responsibly. Without this, we cannot expect young people to grow up with a sensible attitude towards alcohol.”