Serious injuries or other life-threatening warning signs have been detected on 285 occasions when children have been physically restrained in privately run jails over the past five years, according to Ministry of Justice figures.

The figure reflects the number of "exception reports" submitted by the four privately run secure training centres to the youth justice board since 2006.

The warning signs triggering an exception report include struggling to breathe, nausea, vomiting, limpness and abnormal redness to the face.

Serious injuries are classified as those requiring hospitalisation and include serious cuts, fractures, concussion, loss of consciousness and damage to internal organs.

The MoJ figures, which have been disclosed for the first time, show that there were 61 such exception reports made last year. There have been 29 so far in the first 10 months of this year.

Their disclosure comes as a two-day High Court challenge is due to get underway over the MoJ's refusal to identify and trace hundreds of children who have been unlawfully restrained in the privately run child jails using techniques that have since been banned. Children's rights campaigners believe they should be entitled to compensation.

The Children's Rights Alliance for England (Crae) has brought the case challenging the justice secretary, Ken Clarke's, refusal to contact former detainees dating back to 1998, when the first secure training centre opened. The legal challenge follows a second inquest earlier this year into the death of 14-year-old Adam Rickwood, who was found hanging in his room at Hassockfield Secure Training Centre, where he was on remand in 2006. It concluded there was a serious system failure which gave rise to an unlawful regime at the child jail.

The use of several "distraction" restraint techniques, that involved inflicting pain with a severe blow to the nose or ribs, or by pulling back a child's thumb, were banned in 2008. The use of physical restraint techniques to control teenagers simply for the purposes of "good order and discipline" was also ruled unlawful by the court of appeal.

Carolyne Willow, Crae's national co-ordinator, said their lawyers will argue there had been a chronic failure by the authorities to protect vulnerable children over many years.

"It was not children's responsibility to know about, challenge and stop unlawful and abusive treatment," said Willow, adding there were potentially thousands of former detainees who should now be contacted.

"Children in custody are among the most disadvantaged in society and they were held in closed institutions where unlawful restraint was routine and ordinary. It was the state, and the private contractors, who were duty-bound to protect the welfare and rights of vulnerable children."

She said that government officials now had a duty to notify potential victims that their rights had been infringed. The abuses should no longer remain hidden and unchallenged.

The security company, G4S, which operates three of the four child jails is also joining the case as an 'interested party'.

The MoJ has maintained that it has no duty to notify former detainees and insisted that safety of young people in custody has always been its highest priority. The MoJ has previously said that restraint is only ever used as a last resort when young people put themselves or other people's safety at risk.

The justice minister, Lord McNally, has told peers that the 285 exception reports since 2006 were submitted by secure training centres if any warning signs or serious injuries were detected during or following the use of physical control in care - as the current system of restraint is called.

He said they were used to gather evidence and enable the incident to be reviewed by the youth justice board to identify ways of improving the safety and efficacy of restraint methods.

The exception reports are passed to a panel, which includes medical experts, who consider every case and are able to report to ministers any significant issues, said Lord McNally.