Young people at Huntercombe Young Offenders' Institution near Wallingford have been kept in solitary confinement naked and without light, ventilation, sanitation or furniture.

Strip cells -- described by prison reformers as barbaric -- have been used 152 times nationally over the last year.

Huntercombe came top of the list by using them 46 times.

The Howard League for Penal Reform is investigating the use of the cells, which are outlawed by human rights legislation.

The Home Office, which released the figures, insisted they were only used in extreme circumstances for segregation, and not punishment.

No-one at Huntercombe would give an official response to questions of why the strip cells were still in use or for what reason young people were locked up in solitary confinement.

No one from HM Prison Service was available for comment yesterday.

Prisons minister Paul Goggins told Parliament in December strip cells could be used only for temporary confinement of a "violent or refractory" prisoner and not as a punishment.

He added: "As soon as the original justification for the use of special accommodation has ceased, the young person will be removed."

A spokesman for The Howard League called for the practice to stop.

He added: "You have to treat children with decency if you want to change their behaviour. Children in prison may be offenders, but they are still children."