A High Court judge on Thursday ruled the UK government's long-term use of hotels to house lone child asylum-seekers has been unlawful over the last 18 months.
The charity Every Child Protected Against Trafficking (ECPAT) sued the interior ministry over the practice of housing unaccompanied youngsters in department-run hotels.
The organisation argues the arrangements are "not fit for purpose".
In a 55-page ruling, Judge Martin Chamberlain said the practice was "unlawful" and should only be used for "very short periods in true emergency situations".
He noted it had become "systematic and routine" since December 2021 and that interior minister Suella Braverman had "exceeded the proper limits of her powers" in allowing it.
"It cannot be used systematically or routinely in circumstances where it is intended, or functions in practice, as a substitute for local authority care," he added.
Britain has been grappling with how to house tens of thousands of asylum-seekers, who arrive on its shores each year, while their applications are considered.
Under UK immigration law, central and local governments are required to provide accommodation to all asylum-seekers, who are not allowed to work while they await decisions on their cases.
That includes thousands of children who have arrived unaccompanied across the Channel in small boats in recent years, with the government's increasing use of interior ministry-run hotels widely reported.
In a sign of the perils of the policy, Immigration Minister Robert Jenrick revealed earlier this year that 200 such children -- 13 aged under 16, and one a female -- had gone missing.
In an apparent update on that number, the High Court heard this month that 154 children remained missing from the hotels, including a 12-year-old.
In his ruling Thursday, Chamberlain singled out Kent County Council for acting unlawfully in failing to accommodate and look after lone children seeking asylum when notified by the interior ministry to do so.
He accused the council of choosing "to treat some unaccompanied asylum-seeking children differently from and less favourably than other children, because of their status as asylum seekers".
At a subsequent hearing after issuing his ruling, he said there was an "urgent" need for "negotiation" between the ministry and Kent's local authority to resolve the situation.
An interior ministry spokesperson said it will "continue to work with Kent County Council and local authorities across the UK to ensure suitable local authority placements are provided for unaccompanied children".
