Sinn Féin MLA Maeve McLaughlin has called on the health minister to explain why more than 100 children have not been allocated a social worker in the Western Trust.
Speaking after meeting social workers, the chair of the Assembly's heath committee and Foyle MLA said;
"A child is said to be accommodated by the Trust when he or she is looked after in a foster home or children's home for more than 24 hours.
"Normally between 400 and 430 are formally accommodated in the Western Trust area but this year it is 523.
"That means there are more than 100 cases where children have not been allocated a social worker.
"The system is currently so busy that staff have told me that the department is 'running hot.'
"The Trust has appointed eight new social workers for children at risk but there is still a backlog at present.
"There are two specialist care placement schemes available which deliver a high level of care, one in England and one in the 26 Counties, but the costs can be prohibitive.
"I have written to health minister Edwin Poots outlining my concerns about the high number of children formally accommodated in the Western Trust and the resources in place to deal with the situation.
"I will also be going on a placement visit with social workers to see at first hand the challenges that exist in the current system."