Social workers in Slough are failing to look after the needs of some of the town's most vulnerable children, according to its latest Ofsted report.
An inspection last month found there were "significant failings" in how the council monitors children at risk.
Ofsted officers found during a random check that one child was at risk from an abusive parent.
Children's Services director Clair Pyper said it needed help from the government to recruit social workers.
The authority was given an "adequate" rating for how it looks after children in care.
In one case the risk to the child was so great an abusive parent had to be removed from the home.
The report said in this case: "Poor practice was neither identified nor challenged and led to children experiencing ongoing risk of serious harm."
It also said there were failings in Children's Service's contribution to child protection work, particularly with regards to children who had already been identified as suffering, or at risk of suffering significant harm and were the subject of child protection plans.
The council said since the inspection it had audited every single case of children under five at risk.
A council spokesperson said: "We do not believe this is a systemic failure, but is about fine judgement by staff and insufficiently robust and challenging oversight by managers."
According to the council, the "risk of suffering significant harm" mostly applies to children living in households where there is domestic abuse between their parents.
"All of those children are still with their parents because they didn't meet the legal threshold to remove them from their parents," she said.
"The children weren't injured.
"Ofsted have picked up some management, supervision and quality assurance areas that we really need to work on. Since the Ofsted visit that work has been going on."
Ms Pyper said she was "hugely distressed" by the finding and added there had been a huge increase in the demand for social work services.
"We have a third more children in child protection plans than we had just over a year ago, we have twice as many children in care as we had three years ago, and we've had no extra funding from government to deal with that," she said.
"We actually look after children in care well. We need help from government to train and continue to recruit social workers."
The council said it had recruited eight extra social workers in the previous week.