Rikki, six, was found strangled to death near his home in Peterborough, Cambridgeshire, two years ago. His mother, Ruth Neave, 28, was found not guilty of his murder last October, but jailed for seven years for cruelty.
Joanne Kaye-Smith, regional officer for Unison, said the county council had commissioned the report from the consultancy The Bridge, and set the parameters. She said researchers did not interview any of the social workers involved. Rikki's aunt, Sandra Chesney, said no member of the family had been involved.
A county council spokesman stressed the report was independent, and said: "There have been interviews with 17 present and former members of staff."Reuse content