Services for child asylum seekers are at "breaking point" in one of Britain's main gateways and the situation is unsustainable, council officials have warned.
A total of 980 unaccompanied asylum seeking children (UASC) are now in Kent County Council's care - up from nearly 630 at the start of August.
Most are 16 and 17-year-old boys who have been smuggled across the English Channel, placing pressure on local authority services in Kent as well as on the police and local NHS, a report said.
Migrants have surged into Europe from countries in north Africa and the Middle East, with many ending up in Calais where a 6,000-strong migrant camp dubbed Jungle II is based.
The Kent County Council report said the "unprecedented" influx of UASC was having a negative impact on "citizen" children the local authority is already supporting.
While praising staff, the report said: "It should be stated clearly that services are at breaking point and the current position is not sustainable."
Mounting pressure was being faced by staff to meet statutory requirements, including completion of visits, health assessments and reviews.
A total of 180 UASC are without a social worker and waiting a full assessment in Kent and "gateway" authorities like Kent, Croydon and Hillingdon were facing "unreasonable" and "excessive" burdens during crises.
Under the Children Act 1989, it is a council's legal responsibility to care for under-18s who arrive in their local authority area from abroad, seeking asylum.
Help to deal with the influx of UASC has been sought by Kent County Council from other local authorities, with 19 agreeing to take full responsibility for 49 youngsters.
Some children have had to be placed in areas as far away as Hertfordshire, which officials said complicated delivery of assessments and support for them.
The crisis has also forced the council to hire more than 20 extra social workers, three team managers and a service manager since June.
Urgent steps were being taken to recruit more social workers, but challenges were being faced finding qualified, experienced staff in Dover or west Kent, the report added.