Social workers failed properly to follow up child abuse allegations about a baby from Swansea who was later murdered, a report has found.
Eight days before Aaron Gilbert was killed by his mother's partner in May 2005, an anonymous caller complained about the way he was being treated.
Instead of an investigation, a letter was sent to Aaron's mother, Rebecca Lewis, but went to the wrong address.
Lewis was later convicted of familial homicide for failing to protect Aaron.
Last year, she became one of the first people in the UK to be convicted of the offence after a jury found her guilty of failing to prevent partner Andrew Lloyd from murdering baby Aaron.
Lloyd admitted the murder and was jailed for 24 years, while Lewis was jailed for six years.
A review has been carried out by the Local Safeguarding Children Board (LSCB) into the involvement of all local services leading up to the murder.
It calls for a review of the department which took the anonymous call claiming Aaron had bruises and was being cared for by people who possibly had problems with drugs.
The details of the call were passed on to a social worker, who wrote a letter to Lewis inviting her to a meeting.
However, it was sent to the wrong address and Lewis did not turn up.
On the same day in an unrelated visit, a health visitor called at their house and left a card.
But later that day, 13-month-old Aaron was admitted to hospital suffering from head injuries from which he never recovered.
He had 50 injuries on his body when he died of brain damage in May 2005, it emerged during the trial at Swansea Crown Court.
The report concludes that sending a letter was an "inadequate response" to the allegations.
It says the social worker was not properly supervised because key staff had left and had not been replaced immediately.
There were also problems about the way information about Lloyd was shared and he was not identified as a "significant risk".
Details of his parole licence were not put on police computers, mental health services did not pass on information about his personality disorder and his history of domestic violence was not shared with the probation service.
The report found work of the health service was "largely very positive"
But on one occasion his mother took Aaron to hospital with an injured arm and left before being seen.
Staff decided a home visit was needed, but it never took place because of staff sickness. The report adds that, while many of the circumstances which led to Aaron's death could not have been predicted, lessons must be learned by everyone involved in the case.
This included Swansea social services, the Probation Service, the NHS and South Wales Police.
LSCB chairman, Mark Roszkowski, said: "We welcome the review as a means for all the agencies involved to identify lessons that need to be learned to improve interagency working and better safeguarding for children."
The child and family division of Swansea social services said it had carried out its own examination and had already implemented many of the review's recommendations.
It said it would be working closely with its partners to further improve procedures in the interest of vulnerable children.
Swansea Health Community said it was important that agencies involved in child care worked together to avert tragedies like Aaron's death, and an action plan was in place to further improve procedures.
South Wales Police said they had already taken steps to act on some of the recommendations and would "continue to work with our partners to identify those who pose a risk to society and protect those who are vulnerable."
A Welsh Assembly Government spokesperson added: "The Welsh Assembly Government will read the report thoroughly and will consider the lessons that can be learnt in this tragic case."