A young offender institution has been damned as dangerous, riddled with violence and the youths out of staff control in its latest inspection.

In six months up to March this year there have been 61 assaults and 92 fights, some of which were very serious, at HMYOI Cookham Wood. They included head injuries and wounds that required hospital treatment.

The prison holds boys aged 15 to 18, and for the first time ever in its history, 10% of the 166 boys have been incarcerated for murder or manslaughter.

According to Nick Hardwick, Chief Inspector of Prisons, handling these criminals positively is challenging and staff should have significant skills and experience; yet a quarter of all staffers were on detached duty and many of them did not know the work, the institution or the boys.

“A much wider political and policy response is needed if we are to fulfil our responsibilities to care for these, our most damaged children" - Nick Hardwick, Chief Inspector of Prisons

A recent search recovered 15 improvised weapons just one wing of the prison.

During the visit in May Mr Hardwick also found the level of violence had soared and while officers were caught on CCTV “responding bravely to protect boys from attacks”, staff assaults had almost doubled.

There were 21 staff assaults, some resulting in serious injury, up to March 2015.

Force had been used against boys 400 times in six months, compared with 282 during the six months before.

Staff also used techniques to inflict pain, but not all of them were recorded and three boys had required hospital treatment after being restrained.

Some of the other boys in the institute have also been left to live in fear, with 41% saying they felt unsafe - compared with 27% at the last inspection.

Over a third of the boys stayed locked in their cells during most of the day, as many were too frightened to mix with others.

Some of them had no other choice, as activities wanted to do were cancelled and they were prohibited from contact with other prisoners.

There were too few opportunities for the youngsters to access educations and activities or take on paid work or work experience because of the security restrictions.

Mr Harwick said: “Behaviour management processes were weak and low-level poor behaviour was not promptly challenged and so it escalated, while good behaviour was not publicly recognised so there was little incentive to behave well.”

He added: “Cookham Wood reflects the systemic problems we have identified across the YOI estate.

The welcome fall in the number of children in custody means that those who remain represent a more concentrated mix of very challenging young people, held in a smaller number of establishments that are increasingly unsuitable to meet their needs, and cared for by a staff group beset by shortages and a lack of training for their complex and demanding role.

“A much wider political and policy response is needed if we are to fulfil our responsibilities to care for these, our most damaged children, safely and help them to grow into adults who are valued, not feared.”

There have been improvements in the institution in some areas.

Levels of self-harm had fallen, health care was better provided including to those with complex needs, work on equality and diversity issues had improved, although there was still more to do; and for boys who did get access, the overall effectiveness of education, learning and skills was good.

Staff are now in the process of being better training in restraining the boys where necessary.

Andrew Neilson, director of campaigns at the Howard League for Penal Reform, said: “This is a shocking report.

"Child prisons like Cookham Wood do not have the overcrowding pressures that we see in adult jails, and yet there are similar problems – violence, bullying and prisoners spending hours on end locked in their cells.

"It highlights the extent to which this model is failing troubled children.”