Vulnerable children who arrive in Britain by small boat are being placed in an adult prison that holds significant numbers of sex offenders. A growing number of cases have been identified where unaccompanied children, many of whom appear to be trafficked, have been sent to HMP Elmley, Kent, and placed among foreign adult prisoners. According to the most recent inspection of Elmley, the block where foreign nationals are held also houses sex offenders. Of 14 unaccompanied children so far identified by staff at Humans For Rights Network as being sent to an adult prison, one is believed to have been 14 when they spent seven months in Elmley. Most of the cases involve Sudanese or South Sudanese children who travelled to the UK via Libya, with most appearing to have been trafficked or having experienced some form of exploitation. This weekend there were calls for the Home Office to launch an immediate investigation into the issue and urgently release anyone believed to be a child who is inside an adult jail. Maddie Harris, of Human Rights Network, said the group had worked with more than 1,000 age-disputed children and that those sent to adult prisons were among the most “profoundly harmed”. She said: “These children are locked down in their cells, not knowing who to call for help, prevented from adequately accessing legal advice and from challenging the arbitrary decision made about their ages by immigration officials upon arrival in the UK. These are children looking for safety who instead find themselves in an adult prison, denied that protection and exposed to great harm.” Anita Hurrell, head of the migrant children’s project at the children’s charity Coram, said: “It is wrong to criminalise these children and dangerous to send them to adult men’s prisons.” The children – whose ages are contested by the Home Office – have been charged with immigration offences introduced under the Nationality and Borders Act, which became law last year and introduces tougher criminal offences to deter illegal entry to the UK. Lawyers warn that the practice of sending unaccompanied children to adult prisons appears to be increasing. On Thursday, an age-disputed child was identified in Folkestone magistrates court bound for prison, and there were reports that another minor was in police custody in Margate and also expected to be sent to Elmley. The imprisoning of minors is, say critics, the latest facet of a broken asylum system. On Thursday, the asylum backlog rose to a high of more than 175,000, up 44% from last year, despite government spending on asylum almost doubling. The children sent to Elmley were declared adults by the Home Office following what many experts describe as a “cursory and arbitrary” age assessment by officials, often conducted within hours of them reaching the UK by small boat. A number of Home Office decisions that meant children were sent to an adult prison have already been overturned after detailed assessments by independent or local authority specialists. New data obtained by the Observer confirms that hundreds of asylum-seeker children are being wrongly treated as adults by the Home Office. According to data from dozens of councils, more than half of the unaccompanied asylum-seeking children who undergo Home Office age assessments on arriving into the UK are later confirmed to be children. Data from 55 councils under freedom of information laws shows that of 1,416 age assessments carried out over the five years to April 2023 by specialist social workers on age-disputed asylum seekers, 809 were found to be children. In 10 councils, all of the young people assessed were found to be children. Syd Bolton, co-director of Equal Justice For Migrant Children, said: “Age assessment has developed into the most monstrous of procedural devices.” Bolton said he considered the practice to be a “deliberate barrier to accessing asylum protection and denying young asylum seekers access to children’s services. It is a major tool of the Home Office in discrediting an asylum claim.” Wrongly classifying children as adults means they can also be placed alone in unsupervised accommodation alongside adults. In Elmley, Harris said, youngsters shared cells, although a number of age-disputed children had since been released. According to Elmley’s latest inspection, one in four inmates in a survey said they felt unsafe in the jail. It also said that, despite the prison being “no longer designated to hold prisoners convicted of a sexual offence”, 70 such inmates were still there. Days ago, details emerged of a paedophile being held at Elmley who was convicted of 14 sex offences and found guilty of abusing two children. Harris added: “The children are always deeply harmed by the time they have spent in prison in the UK, expressing clearly how they are unable to sleep, do not understand why they were held there and struggle to speak about their time there.” She added: “It should be made clear that neither adult or child should be criminalised for arriving in the UK to claim asylum, an offence that clearly contravenes the refugee convention.” Hurrell referred to a recent court ruling that unaccompanied minors should be looked after by councils “where they can be kept safe and recover”. It is thought that many more unaccompanied children have been placed in adult prisons. Human Rights Network staff attending hearings at Folkestone magistrates court have identified them by noticing a young person contesting the date of birth given to them by immigration officials upon arrival in the UK. A government spokesperson said: “Assessing age is a challenging but vital process to identify genuine children and stop abuse of the system. We must prevent adults claiming to be children, or children being wrongly treated as adults – both present serious safeguarding risks. “To further protect children, we are strengthening the age-verification process by using scientific measures such as X-rays.” The spokesperson added that the government had not been provided with the information needed to investigate the points raised by the Observer, although at the time of publication it had not asked to view any evidence.