The way some teenage detention centre inmates were treated in the 1970s and 1980s could be officially classed as torture, a leading child abuse lawyer has said.
David Greenwood, who has acted for victims of the Rotherham abuse scandal, is calling for a public inquiry into what went on behind bars in institutions across the country up to 40 years ago.
He said the UK signed up to the UN Convention Against Torture in 1984, but young inmates were subjected to cruel, degrading punishments even after that point.
Often the crimes they committed would these days warrant a community punishment.
Seven former prison guards at a detention centre in northern England are currently being prosecuted following allegations of sexual and physical abuse.
And Mr Greenwood has worked with other claimants who were locked up at different institutions who allege they were tortured.
The solicitor said: "These young men were a forgotten segment of society and people viewed them as worthless.
"It was torture and in any prison, in any battlefield, it would not be tolerated, yet it was systematic in our detention centres in the 1970s and '80s."
Mr Greenwood, a director of Switalskis Solicitors, said: "These boys were locked up, they could not run away but were subjected to what I would describe as torture from prison officers.
"I submitted a complaint to the UN concerning this and the UK's lack of adherence to the convention in this regard. I am still waiting to hear from the UN officials in charge of monitoring."
Mr Greenwood said ex-detainees have told him they were routinely punched by staff.
He said: "The use of stress positions was universally applied, having to bunny hop in a fully crouched position from one place to another without using arms to steady yourself was usual."
Home secretary Willie Whitelaw's Short Sharp Shock initiative, where inmates were given a burst of Army-type discipline was taken too far by some officers, Mr Greenwood said.
Leading criminologist Professor David Wilson was governor of a more progressive young offenders' institution in the 1980s.
He said detention centres were run to deliberately put inmates under psychological and physical stress.
"That line between putting someone under stress and simply brutalising them seemed to never be clearly enough drawn," he said.
"The Short Sharp Shock was clearly going to be interpreted by some members of staff in ways that would lead to abuse."
Inmates at Eastwood Park Detention Centre in Gloucestershire have told Mr Greenwood they were punched if they did not answer officer's responses with "Sir".
The lawyer added: "They would be regularly punched for the slightest misdemeanour and were also whipped with a length of rubber pipe."
A poem written by an ex-Eastwood Park inmate refers to being made to stay in a sitting position but without being allowed to use a chair.
Cleveland Police have been investigating historic allegations about Kirklevington Detention Centre near Yarm.
So far more than 400 complainants have come forward, the force said.
Mr Greenwood, who represents around 50 of them, said: "The same type of abuse is complained of - punches for no reason, stress positions, cold showers, prolonged physical exercise.
"I have received similar reports of similar extreme physical abuse from staff at Thorpe Arch Grange in Yorkshire dating back to the 1980s."
He said these men, now in their 50s, deserve compensation and answers.
"I am working with a group of the men to call for a full public inquiry into the treatment of our young people by prison staff in the 1970s and 1980s," he said.
"I hope to influence the Home Secretary to order an inquiry."
A Prisons Service spokesman said: "There is already an inquiry looking into these allegations, which is part of the Independent Inquiry into Child Sexual Abuse."
He said it would be inappropriate to comment on allegations of abuse at a specific detention centre which were subject to an ongoing police investigation.