Figures emerge in critical letter to Home Office from organisation appointed to scrutinise detention facilities

Nearly 100 children have been wrongly identified and detained as adults under Shabana Mahmood’s “one in, one out” deal with France, the Guardian can disclose.

Home Office staff said that of 304 age-disputed cases arising from the scheme over nine months, 94 (31%) – were ultimately found to be minors. Children are supposed to be excluded from the scheme, while government policy limits immigration detention of unaccompanied children to 24 hours.

Had been awaiting deportation for more than six months, despite being supposed be held for up to 28 days only “in exceptional cases”.

Were being readied for removal to France despite having TB or requiring hospital treatment.

Faced removal after being separated from family members with whom they had travelled, which she said had a “particularly damaging impact”.