Children's services at Tameside Borough Council were rated inadequate in December 2016 with a lack of sufficient workforce capacity cited as a "primary contributory factor" to poor practice.
A year later a monitoring visit in October 2017 concluded the pace of change at the authority was "too slow".
And the latest monitoring visit, conducted on 22 August 2018 found staffing issues continue to dog progress.
In a letter to the council outlining the findings, the inspectorate said actions taken by the council to strengthen management had led to a period of instability, with a team manager, practice managers and a number of social workers leaving as a result.
"The difficulty in trying to secure a stable workforce is the local authority's biggest challenge," the letter states.
"Strategic leaders recognise this and are making every effort to recruit permanent staff with the relevant skills and experience to support children."
Ofsted said that although children's services had made 17 recent appointments and shortlisted a further 15 for interview, 41 per cent of staff are still agency workers. Inspectors also criticised the quality of managers' work.
"Management oversight by frontline managers lacks rigour and consistency and is not focused on driving improvements in the quality of practice," the letter states.
Inspectors raised concerns that supervision for social workers was either not taking place regularly, or not being recorded.
Where they were recoded, inspectors said they did not provide "an analytical overview of the children's case, clear case direction or demonstrated reflective practice".
However, inspectors noted that the authority is trying to address the issue by providing workers with individual support and coaching, a management development programme and a supervision tracker.
And, in terms of the care provided to children, inspectors were positive about council workers using an appropriate threshold to bring children into care.
"No children were seen who should not have come into care, and children were safeguarded effectively," they said.
They also praised recording in case notes for their timeliness, and aid case summaries were generally up to date.
But the inspection summary described child and family assessments and plans as weak.
"Assessments are not routinely updated to reflect changes in a child's circumstances," it said.
"This means that planning for the child is based on out-of-date information and the child's plan is not reflective of their current situation."
Inspectors also flagged issues around caseloads. Although the average caseload was 18.5, some social workers reported having as many as 28.
A Tameside Council spokeswoman said that social worker recruitment was one of the authority's biggest challenges.
"Ofsted recognise we are making every effort to recruit permanent staff with the relevant skills and experience to support children and this is now showing some positive results. This remains at the top of our key priorities," she said.
"We accept the pace of improvement in our service for looked-after children has been too slow since the inspection in 2016 and that there was a lack of progress last year," she continued.
"At this point the quality of social work practice and management oversight is too variable. However, as acknowledged by Ofsted, we now have plans in place to address this"
"We accept Ofsted's findings in full and are pleased that they recognise we continue to make progress in improving services for children in Tameside."