Home Office figures show some young offender institutions are among the most dangerously overcrowded prisons in England and Wales, the Prison Reform Trust has claimed.
The charity said the figures showed 27 prisons were operating beyond their safe overcrowding limit.
These included Glen Parva and Lancaster Farms young offender institutions, plus Altcourse, Parc, Chelmsford, Guys Marsh and Bristol prisons, which combine adult and juvenile custody.
Cookham Wood and Downsview women’s prisons were also among the most overcrowded settings.
Prison Reform Trust director Juliet Lyon said the government had become “complacent about overcrowding” and the prison population was “mushrooming out of control”.
The number of people locked up in England and Wales on 30 June was 78,454, two per cent more than the figure a year earlier, according to other recent Home Office figures
More than 2,900 of those were juveniles, while 4,602 were females.