The proportion of young Muslim men in youth jails in England and Wales rose by more than a quarter last year, figures showed on Friday.
One in five males (21%) in young offender institutions (YOIs) identified themselves as Muslim in 2011/12, compared with 13% in 2009/10 and 16% in 2010/11, the annual review of children and young people in custody showed.
The proportion of youth offenders in custody from black and minority ethnic communities also rose slightly to 42%, from 39% in 2010/11, according to the report by the chief inspector of prisons.
The study, published jointly with the Youth Justice Board (YJB), showed the total number of young people in custody fell by 14% last year.
Some 1,543 teenagers, aged 15 to 18, were held in YOIs by the end of 2011/12, compared with 1,822 the previous year.
Around half (53%) of young men said that it was their first time in custody.
Now 231 young offender places have been decommissioned to reflect the decreasing size of the population.
Nick Hardwick, the chief inspector of prisons, has now called on young people's perceptions of their experiences in custody to help shape youth justice policy.
He voiced concern that the proportion of young people who had felt unsafe at some time in custody had risen from 27% in 2010/11 to 32% last year.
A quarter (25%) of young men said they had been victimised by another young person at their establishment and 23% said they had been victimised by a member of staff.
Only 56% of young men felt that they would be able to tell someone they had been victimised and just 28% felt it would be taken seriously if reported.
Meanwhile, almost a third of the young people surveyed (30%) said they had previously been looked after by a local authority.
Mr Hardwick said the figure was "depressingly high" and "reflected the over-representation of children from care in almost every indicator of disadvantage for decades".
The study was based on the experience of 926 young men in eight male establishments and 25 young women in three female establishments in which they were held from April 1, 2011 to March 31, 2012.
Mr Hardwick said: "It might have been expected that reductions in the number of young people held and changes to the custodial estate would have led to changes of similar significance to young people's perceptions of their experience in custody.
"In fact, it is striking how little has changed and that may cast doubt on the assumption that, as the population decreased, it would include a greater concentration of young people with a serious offence background and major problems.
"Young people's own perceptions of their experience in custody, their hopes and concerns, should be an important part of the evidence that shapes the future of the youth justice custody estate and youth justice policy.
"These annual surveys provide an important resource for tracking these perceptions and identifying progress made and work still to be done. The voice that comes through these statistics is largely realistic but hopeful - and should not be ignored."
YJB chair Frances Done said: "Children in custody are amongst those with the very greatest needs and and their safety and welfare is our highest priority.
"We commission this report each year to help us to identify the progress made and areas which need further improvement.
"Our overriding objective is to ensure that whilst in custody children are kept safe, supported to address their offending behaviour and helped to lead successful lives on release.
"We will review the findings of this report and work with our secure establishments to ensure that they are taken into account in all aspects of their work."
Andrew Neilson, the Howard League for Penal Reform’s Director of Campaigns, told The Huffington Post UK: "The increase in the proportion of boys in custody who describe themselves as Muslim mirrors a trend also seen in the adult prison population.
"It only emphasises the need for the government to carry out detailed research into why this trend is happening."