The figure is up 34 per cent from the previous year, when numbers dropped by almost a fifth during the coronavirus pandemic, and represents a rise of 10 per cent from March 2020.
UASC now represent 7 per cent of all looked-after children — up from 5 per cent last year and 6 per cent in 2018.
Most are boys (95 per cent) and 13 per cent were under 16.
Under the now-mandatory National Transfer Scheme, councils around the country share the responsibility for looking after unaccompanied children.
In 2022, the local authorities that were looking after the most UASC were Kent (370), Hillingdon (139) and Manchester (138).
Overall, there were 82,170 looked-after children in England in March — up 2 per cent in a year.
More than half were male (56 per cent), and 73 per cent were white, while children from black, mixed and other ethnic groups were represented.
Two thirds of children went into care because they were at risk of abuse or neglect.
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Most children were placed in foster placements (71 per cent), secure units, children’s homes or semi-independent living accommodation (16 per cent) or with parents or another person with parental responsibility (7 per cent).
The number of children fostered by a relative or friend has increased by 29 per cent since 2018, and makes up about 15 per cent of looked-after children.
Children in unregulated placements, such as semi-independent living or living independently, have increased by 23 per cent since last year, representing 9 per cent of looked-after children.
Over the year to March 2022, there were 76,890 missing incidents reported concerning 12,150 looked-after children.
Almost two thirds of incidents were children going missing from secure units, children’s homes or semi-independent living accommodation, which is likely to have been due to older children being placed in these settings.
The majority (90 per cent) of missing incidents lasted for two or fewer days.
Councils have a duty to provide accommodation that is in the local authority area, meets the needs of the child and allows them to live near home.
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While the majority of children were placed within 30 kilometres of their homes, more than a fifth (21 per cent) were not.
The figures also show the number of looked-after children who were adopted rose by 2 per cent since last year to 2,950.
The Department for Education describes this as a “modest” increase after a fall of 18 per cent the previous year due to court cases stalling or taking longer during the pandemic.
Councillor Louise Gittins, chairwoman of the Local Government Association’s Children and Young People Board, called the increase in children in care “very worrying”.
“Councils are doing all they can to support vulnerable children and their families but are facing severe financial challenges as well as worsening workforce shortages,” she said.
“This is making it more difficult to support children and families earlier.
“While councils are proud of the support they provide to all those seeking refuge in this country, the sharp increase in unaccompanied asylum-seeking children coming into care reinforces how vital it is that the Home Office fully funds the cost of supporting these children, including when they leave care.”