Children's services at Powys council are set to overspend by more than £6m, councillors have been warned.
Aled Davies, cabinet member for finance, blamed rising costs of agency staff, placements and legal fees.
The authority was plunged into crisis in October 2017 when a damning report by Welsh Government inspectors said failings had put children at risk.
John Morris, who chairs the council's audit committee, said he wanted to see "adequate financial control".
Officials from Care Inspectorate Wales recently returned to Powys to assess progress in a department criticised for missed opportunities to safeguard children, poor risk assessment and serious performance issues.
The ongoing challenges were reflected in a budget update to cabinet by Mr Davies on Tuesday.
It showed that children's services, which have an overall budget of £18m, accounted for the lion's share of a predicted council overspend of nearly £8.7m for 2018-19.
Mr Davies said costs "continue to escalate", with spending on an increased number of placements for looked after children going £3.5m over budget.
Children's services have 14 extra members of staff above the agreed maximum, but the report added that "many posts" are covered by costly agency staff.
Historic savings of £2.2m that the department was expected to make before the crisis are now expected to be wiped out, according to the Local Democracy Reporting Service.
Mr Morris told the cabinet: "We really need to understand that there's adequate financial control in that specific area.
"If you are increasing [the overspend] by £500,000 a month that will bring a significant risk to the council."
Rachel Powell, cabinet member responsible for children's services, said she would be happy to explain the pressures to Mr Morris, particularly about agency staff.
But she added: "We have to be realistic as to what children's services can contend with in view to functioning properly."