Increase of 25% of children in social care in Somerset
The number of children in social care has increased by 25% to 475 since 2009, Somerset County Council has said.
Referrals, where a child is reported due to welfare concerns, have also gone up from 3,500 to 5,500, between 2009-11, and child protection plans have increased by 30% in two years, to 290.
The increase has been blamed on drug and alcohol misuse or parents with "personal difficulties".
The council has spent an extra £3.9m to pay for the increased workload.
The legal costs of care and placements account for a large part of the budget.
The service director for safeguarding and children's social care at Somerset County Council, Linda Barnet said: "Assessments where a parent and child go for a placement can cost £2,500 - £3,000 a week if it's out-of-county with an agency."
"It could be for a period of up to six months but we would try to make those periods for as short as possible and we are developing in-house provision for that."
During assessments, both the parent and child are put under 24-hour observation with a trained foster carer to see whether the child will properly cared for.
Child protection plans, where the child might be taken into care with another member of the family or into foster care, can cost an average of £470 a week in Somerset.
The original budget for children's social services in 2010-11 was £30m.
An extra £3m has been put aside this year which will bring the the total amount spent on children's social care to £33m for 2011-12.