Social workers at an east London council have been criticised by a judge who heard that a baby died only six days after it had been taken off an "at risk" register.
Tyrell Rowe, who was 19-months old, died in hospital on 17 October from brain damage after being repeatedly punched in the face.
The Old Bailey heard that after his death a number of other broken bones were discovered which had been caused in the previous two months.
Hackney Council social services had been supervising the baby, but had not examined him during that period.
On Friday Judge Anthony Morris criticised the council for not making public an internal investigation into the death.
'Lack of protection'
"I find it regrettable because the purpose of such an investigation must be how such failures occurred and to prevent them happening again," he said.
"I am disappointed by the apparent lack of protection given to Tyrell by the social services department."
Sandra Rowe, 29, and John White, 37, Tyrell's parents, had originally been charged with murder.
But, the court was told, the couple from Stoke Newington, north London, could only be prosecuted for child cruelty, alleging that they did not get medical help for his earlier injuries.
White, who pleaded guilty to child cruelty, was given a three-year jail sentence.
Tyrell's mother, who has a low IQ and the reading age of a five-year-old, had been found at an earlier hearing to be unfit to plead.
'Decision to return child'
A jury later found she had committed the act and Judge Morris placed her under a supervision and treatment order with Lambeth social services, south London, for two years.
Tyrell had been under the supervision of Hackney social services since his birth, but was removed from he child protection register six days before his death.
After the case, Hackney Council said: "The death of any child is a tragedy. This is especially so in Tyrell's case where a wide range of professionals and the courts were involved in the decision to return the child to his parent's care.
"The Area Child Protection Committee is concluding its investigation. Recommendations will be implemented by the respective agencies.
"Appropriate action will be taken as required if individual failings are identified."