Following their second monitoring visit to Reading Borough Council's children's service the inspectorate found management has not been focused enough on improving the quality and impact of social work with children and their families.
As a result, children in need are not being visited within stipulated timescales, with a third of home visits overdue and a similar proportion of children left without a written plan.
In one instance a case was closed after only a single home visit within a four-month period. Records of home visits are often unaligned with children in need plans and assessments lack clarity, inspectors also found.
"This means that many parents and children do not understand the aim of the social worker's work or what needs to change," a letter outlining the findings of the monitoring visit said.
Caseloads have reduced for many social workers, but inspectors found that some are still higher than the reported average of 22. Ofsted has warned the council that lower caseloads are crucial to retaining staff.
At the time of last month's visit, the proportion of permanent social workers at the council had increased to 62 per cent, but this was only a "small improvement" since Ofsted's last visit.
Ofsted found 15 cases where no social worker had been allocated, which "indicates that ongoing turnover of social workers continues to have a detrimental impact on the consistency of work with a small number of children and families".
Inspectors are particularly concerned that most team managers are temporary workers, indicating "continuing fragility in the spine of the frontline workforce".
Another problem highlighted was that strategy meetings for children at risk of significant harm were often just telephone discussions between social workers and police and did not involve other agencies working with families.
Ofsted also found that for too long the senior management team did not have an "agreed and consistent position" on how to improve services.
This was not addressed until December when Ann Marie Dodds was appointed acting director of children's services.
But still the children's services department does not have "effective internal quality assurance measures", inspectors said, with the council instead relying on external auditing.
Despite the concerns the inspectorate found no cases of children at immediate risk. Ofsted also noted progress in improving return home interviews when children go missing. These are completed quickly and staff involved were praised for being "tenacious and creative in engaging young people".
Reading's children's services was handed Ofsted's lowest rating last August after inspectors found children being left too long in "situations of unknown and acute risk".
A month later Nick Whitfield, chief executive of Achieving for Children, the community interest company that runs children's services in Kingston upon Thames and Richmond, was appointed as commissioner to review whether control of children's social care should be taken away from the council.
A Reading Borough Council spokesman said: "The council fully accepts the findings of the Ofsted monitoring report. Managers and staff within children's services have been working tirelessly to address the issues identified by the full Ofsted inspection of the service in August 2016, which resulted in an ‘inadequate' rating."
He added that "the council fully recognises the service still has a long way to go" and will continue working closely with Whitfield to address Ofsted's concerns.