Blackpool Council is “inadequate” at caring for some of the most vulnerable children, a report has found.
The standard of child protection at 20 councils - including Blackpool - is “unacceptably poor”, Ofsted has warned.
Only one in four local authorities are judged to be “good” at safeguarding children, a new report by the watchdog has concluded.
A spokeswoman for Ofsted said the report was looking back at previous inspections including Blackpool’s which was published in July last year.
Since then the council has been working closely with the department of education on measures to improve child protection in the resort.
Coun Sarah Riding, cabinet member for children and young people, said changes including early intervention and multi-agency working were having a positive impact on children’s services.
Ofsted, which inspects children’s social care including child protective services, said more needs to be done to address “incompetent and ineffective” leadership in children’s services.
Some managers do not have a “firm understanding” of what constitutes good practice, the watchdog said.
In its first stand-alone social care annual report, Ofsted said that children’s services need “strong and stable leadership” to improve the services that provide help, care and protection to children at risk of abuse or neglect.
Inspectors found that in the weakest places many “basic acceptable practices” were not in place and some authorities were criticised for poor coordination with health workers, police and schools.
HM chief inspector Sir Michael Wilshaw said: “As it stands today, there are 20 councils where the standard of child protection is unacceptably poor and judged to be inadequate.
“Incompetent and ineffective leadership must be addressed quickly. But where those in leadership positions have capacity and potential, this must be recognised and nurtured.
“Too much leadership volatility in social care is counter-productive - that goes without saying. One in three local authorities has had a change in their director of children’s services last year alone. The combination of unstable communities and political and managerial instability in our social care services is a dangerous mix.”
Ofsted’s national director for social care, Debbie Jones, said: “The picture of performance we are publishing today shows there is clearly an ongoing need for improvement.
“Some services are increasingly expert at reducing risk, helping families to look after their children and enabling children at risk in their area to make good progress.
“It can be done, and therefore it must be done in all areas, equally well. Ofsted will be rigorous in holding local councils and social care providers to account but we will also support them to make the improvements that children deserve.”
SEE THE GAZETTE ON WEDNESDAY FOR THE FULL STORY AND REACTION.