Nearly 100 people who were detained as adults under the UK’s migration agreement with France were later assessed to be children, raising fresh concerns about safeguarding failures within the government’s controversial returns programme.
Figures provided to independent monitoring bodies show that 94 of 304 people whose ages were disputed under the scheme between August 2025 and May 2026 were ultimately identified as minors. That means children accounted for about 31% of the cases reviewed.
The findings have intensified criticism of the UK’s handling of unaccompanied children arriving through irregular migration routes, particularly those detained while authorities attempt to establish their age.
Under UK policy, unaccompanied children are generally subject to strict limits on immigration detention, while children are excluded from the government’s “one in, one out” arrangement with France.
The figures were disclosed in correspondence from Jane Leech, interim chair of the Independent Monitoring Boards, to Home Office minister Anna Turley. The monitoring boards oversee conditions in immigration detention facilities and prisons.
Leech warned that the current system could be failing to protect people whose ages have not yet been established.
She said some individuals remained in detention for significantly longer than the government’s stated expectation that immigration detention should normally be limited to 28 days, except in exceptional circumstances.
In one case highlighted by the monitoring boards, an individual was held for 27 weeks.
The concerns extend beyond the length of detention.
Leech reported that some people held under the scheme had serious medical conditions, including tuberculosis, while others required hospital treatment. She also raised concerns about people being separated from relatives or others with whom they had travelled before being considered for removal to France.
According to the monitoring boards, such separation could have particularly damaging consequences for vulnerable people.
The UK’s agreement with France, introduced in August last year, permits British authorities to return certain people who cross the English Channel in small boats to France. In exchange, the UK accepts an equivalent number of people from France who have been identified as having legitimate grounds to come to Britain.
The arrangement is intended to discourage irregular Channel crossings by creating a mechanism for some arrivals to be returned to France.
However, the latest figures suggest that the programme has generated significant safeguarding challenges for people whose circumstances or ages are disputed.
Leech referred to the scheme by its Home Office operational name, Operation Hillmore, and said independent monitors had serious concerns about the vulnerability of some of those being detained.
According to her assessment, a number of recently arrived migrants showed signs of psychological distress. Monitoring boards also encountered accounts and documentation indicating that some detainees had survived torture or other forms of abuse.
The handling of age disputes has emerged as one of the most contentious aspects of the system.
In some cases, authorities took more than a month to complete an age assessment. Leech said two cases observed by the Heathrow monitoring board took at least 40 days from the individuals’ arrival at an immigration removal centre before their ages were assessed.
She argued that people whose ages remain uncertain should not automatically be placed in immigration detention while officials attempt to determine whether they are adults.
The concerns are particularly significant because an incorrect assessment can expose children to an immigration detention system designed for adults.
Imran Hussain of the Refugee Council described the figures as disturbing and argued that refugee children were too frequently being treated as adults, potentially exposing them to abuse, neglect and other safeguarding risks.
He called for greater use of professional age assessments carried out by trained social workers, which he said provided a more reliable means of determining whether someone was a child.
The government has defended its approach, saying accurate age assessments are necessary both for border enforcement and to ensure migrants receive appropriate safeguarding and access to services.
The Home Office also said it intends to modernise the process, including plans to introduce artificial intelligence technology to support age assessments from next year.
The controversy comes as the UK continues to face high levels of irregular Channel migration.
Government figures show that 1,087 people were returned to France under the agreement between August 4, 2025 and June 30, 2026.
During the same period, 27,920 people crossed the English Channel to Britain in small boats.
The relatively small number of returns compared with total arrivals has prompted wider debate over whether the agreement is achieving its intended deterrent effect.
For child protection organisations, however, the immediate concern is whether vulnerable children are being incorrectly classified as adults and detained before their circumstances are properly established.
The monitoring boards’ findings also raise questions about the wider conditions in which people are being processed under the agreement, including access to healthcare and the speed with which cases are reviewed.
The reported case involving tuberculosis has added to concerns about medical screening at Manston, a processing facility used for people arriving in the UK.
Leech said one person was transferred from Manston to Gatwick immigration removal centre with tuberculosis, while another person was reportedly refused admission to Brook House because of the seriousness of their medical condition and sent directly to hospital.
The government now faces pressure to demonstrate that the agreement with France can operate without compromising the rights and welfare of vulnerable migrants, particularly children.
The discovery that nearly one-third of disputed-age detainees in the reviewed cases were ultimately found to be minors is likely to intensify calls for safeguards to be strengthened before people are detained or considered for removal.
As the UK prepares to introduce new technology into its age-assessment procedures, the debate over how best to distinguish children from adults is set to remain central to the country’s increasingly contentious migration policy.