Details of the techniques used in a secret manual governing the use of physical restraint in private child prisons have been revealed.
Some of the measures employed in the secure training centres, detailed in the "instructor's manual", include ramming knuckles into ribs and raking shoes down the shins, the Observer reports.
The contents of the manual were revealed after The Youth Justice Board (YJB) agreed to hand over the document earlier this month.
The document includes descriptions of "distraction" techniques, which deliberately inflict pain.
The Observer detailed some of the techniques such as placing an "inverted knuckle into the trainee's sternum and drive inward and upward".
Another practice reads: "Continue to carry alternate elbow strikes to the young person's ribs until a release is achieved."
Children's Rights Alliance for England (CRAE) officials said the YJB initially appealed against an order by the Information Commissioner in December 2009 that the document be given to them.
The CRAE called for the Justice Secretary to order an independent judicial inquiry to examine the regimes of these private child prisons going back to 1998.
Carolyne Willow, national co-ordinator of the CRAE, told the paper: "The manual is deeply disturbing and stands as a state authorisation of institutionalised child abuse."
A Ministry of Justice spokeswoman said the techniques were used "very infrequently", and added: "For young people under 18, the use of restraint is a last resort but where young people's behaviour puts themselves or others at serious risk, staff need to be able to intervene effectively, to protect the safety of all involved."