A re-inspection of children's services at Surrey County Council, where serious concerns about how child sexual exploitation is dealt with were raised following a visit in 2014, concluded that leaders had been "far too slow" to accept and act on the findings and recommendations of that inspection.
"Too many of the most vulnerable children in the county are being left exposed to continuing harm for long periods of time before decisive protective actions are taken," the inspection report states.
Inspectors said children and their families experience repeated assessments and interventions in different parts of the service, often over periods of many years, and they do not achieve sustainable changes.
Frontline managers and social workers were found to not routinely analyse family histories and the "negligible" impact of earlier phases of help.
"This was found to result in children experiencing continued neglectful parenting, often including exposure to domestic abuse, and leaving them vulnerable to both acute and longer-term risk through corrosive damage to their social, emotional, physical and educational development," the report states.
Meanwhile, the quality of assessment, planning and reviewing for children who are on statutory child in need or child protection plans was found to be "too weak".
The understanding and application of thresholds by external agencies was also found to be poor, resulting in too many unnecessary low-level contacts and referrals, overloading social workers in the multi-agency safeguarding hub.
Inspectors said that very recently, leaders, managers and elected members have grasped the scale of improvement needed through an honest acceptance of the depth of practice shortcomings.
This has resulted in a concerted focus on improving children's experiences and outcomes.
"This positive cultural change is starting to build a better understanding of risk, a learning-based practice model and more confident, informed social work with children," the report states.
"However, these improvements are yet to be embedded, and have not yet led to sustained, widespread reform on the scale required for consistently effective and safe frontline services."
Surrey County Council said Dave Hill, a former president of the Association of Directors of Children's Services, has been brought in to lead efforts to turn around provision.
Hill, who helped to turn around services in his previous post in Essex from "inadequate" in 2010, to "good" by 2014, began in Surrey on 30 April.
Clare Curran, Surrey County Council's lead member for children, said: "We totally accept that the support we give to children and their families simply isn't good enough and we've brought in one of the country's most highly-respected children's services directors, Dave Hill, to spearhead the changes we need to make.
"Ofsted recognises we have started the work but much more needs to be done and with Dave in place, we'll build on this, so that support for children in Surrey is as good as it possibly can be."
Dave Hill said: "I'm clear we need to do more to improve the lives of children in Surrey. That's what I've been brought in to do, using the experience I have turning round children's services in other parts of the country. I'm sure we will also do so in Surrey."