The number of times young offenders have been locked up on their own has increased dramatically over the past four years, despite the overall number of children being detained falling, a report found.
The study by the Office of the Children’s Commissioner for England raises questions about whether youth custody is always the most appropriate setting.
The average length of periods of segregation has doubled from eight to 16 days between 2014 and 2018, with 70% of episodes of segregation lasting more than one week.
In one incident a young person was kept in segregation for 100 days due to self-isolation, the report found, and all Youth Offenders Institutions (YOIs) in England reported at least one instance of segregation of 75 days or more.
Children’s Commissioner Anne Longfield is due to present the research to the Human Rights Select Committee on Wednesday.
The findings include accounts of children spending up to 23.5 hours in a cell each day, which the report said would appear to contravene Articles 37 and 40 of the United Nation’s Convention on the Rights of the Child.
One child from a YOI, interviewed as part of the report, told of feeling “upset and anger” at being put into isolation.
They said: “I’ve gone from being out of my pad all day to being isolated, well locked up really, for three days straight, so there was a lot of emotions going through my head. I didn’t really know what was going on.
“I was up and down, I was angry smashing up my pad and stuff like that.
“I ended up tying something round my neck and dropped to the ground.”
The report said that gang involvement, prison staffing levels and shortages of NHS mental health beds may be driving the increased use of segregation.
Mrs Longfield said: “Children tell me that segregation can bring on feelings of stress, apathy, anxiety, anger, depression and hopelessness.
“I want to see more transparency and accountability around the use of segregation in the youth justice system.
“It is extremely worrying that the practice is increasing at the same time as the number of young people in the youth justice estate has fallen.
“I am also very concerned that a child can be separated for 21 days before there is any external oversight.
“We need to ask ourselves why there has been an increase and what changes need to be made to the system to cut down the use of segregation. What does keeping a young person in isolation for 100 days do for their mental health and their behaviour?”
The conditions of separation differ between YOIs, where most periods refer to when a child has been removed to a segregation unit, and Secure Training Centres (STCs), where children are segregated to their rooms or other empty spaces.
Across all YOIs over a six-month period, there were 306 separate episodes of segregation lasting over one week, which compared with the overall number of episodes of segregation is “very high”, the report said.
A Ministry of Justice spokesman said: “The safety and welfare of young people in our care is our priority.
“That is why there are strict safeguards on segregation, which is only used as a last resort when someone is likely to cause harm to themselves or others.
“We are recruiting more staff and investing in enhanced support units for the most vulnerable offenders, so young people have the support they need to turn away from crime and contribute to society.”