Research commissioned by the commissioner, Professor Sir Albert Aynsley-Green, tracked 16 young people in England and Wales who had been admitted to adult psychiatric wards in the last 18 months.

It found many of the under 18-year-olds felt unsafe during their time on adult psychiatric wards.

Some were verbally, physically or sexually harassed from other patients, researchers reported this month.

Other said they were able to take illicit drugs and alcohol.

Staff on the wards lacked experience or training in working with young people and many were not police-checked, said the report, entitled Pushed Into The Shadows.

The report blamed a continuing shortage of hospital beds and services for under 18-year-olds.

The government’s National Mental Health Framework says children with mental health problems should only be put in adult wards in exceptional cases. Ministers say the use of adult wards for children will be eliminated within five years.

Sir Aynsley-Green makes a number of recommendations, including that there be an increase in emergency beds in children and adolescent mental health services, and that staff in adult wards undergo Criminal Records Bureau checks and be trained in working with young people.

Barbara Herts, chief executive of the YoungMinds charity which conducted the research, said: “I hope this report is the spur to ensure that the most vulnerable members of our society are both protected and supported in order that they can achieve their full health and potential.”