The report states that Norfolk County Council does not provide a good enough service for looked-after children and care leavers.
Inspectors also found that at the time of the inspection, in July this year, the local authority had lost contact with 25 per cent of its care leavers, including 26 of its most vulnerable children aged 16 and 17.
Meanwhile 16 looked-after children were found not to have an allocated social worker, and foster carers spoke of their frustration at how hard it is to get a response to queries from some social workers.
"Delays and drift in planning for children are frequently seen in casework, with little evidence of challenge by the independent reviewing service," the inspection report states.
"Planning for permanence, placement choice, health assessments, educational outcomes and access to advocacy services for looked-after children remain weak and, while there is some evidence of progress, this has not been fast enough to secure improved outcomes for most children."
Following Norfolk's previous inadequate rating in 2013, Sheila Lock took over as interim director of children's services from Lisa Christensen. In June this year the authority appointed Michael Rosen to replace Lock.
Ofsted said the impact of the current senior leadership team and elected members has led to improvements in some parts of the service, particularly for children in need of early help and for those children at risk of harm and in need of protection.
"However, despite these efforts, widespread failings for looked-after children and care leavers means that services in Norfolk remain inadequate."
"While improvements have been made in some parts of the service, the senior leadership team know that these are constrained by the scale of the work still required to do," the report states.
Michael Rosen said: “Typically it takes four years to recover from the position that this department was in in 2013.
"It is clear from the report that the department has made substantial progress in what is a relatively short space of time. Sheila Lock, my predecessor, deserves significant credit for the strong leadership that has made this possible."
Rosen pointed to the fact that in 2013, under previously separate inspections of child protection services and services for looked-after children, both areas were judged inadequate.
"The child protection element of the current report shows an improved judgment of 'requires improvement', with inspectors noting that children and young people are now seen and seen alone by their social workers, that the risk of child sexual exploitation is identified well and that when children are identified as at risk, the response is 'timely and proportionate'."