So-called "serious case reviews" are carried out by authorities after a child dies or is seriously injured through abuse or neglect -- as in the high-profile abuse case of Baby Peter.
The death of the 17-month-old after suffering a prolonged period of domestic violence, despite being on a council's child protection register, shocked the nation and threw a spotlight on social services.
Ofsted's latest report, "Learning Lessons from Serious Case Reviews: Year 2" found that out of 173 serious case reviews, 34 percent were judged "inadequate."
Almost a quarter of cases evaluated between April 1 2008 and March 31 this year were judged "good" and 43 percent "adequate."
Ofsted said the figures showed Local Safeguarding Children's Boards were taking a more robust approach in carrying out reviews, but conceded more had to be done.
It also said reviews were being carried out more quickly and that a backlog of cases had been addressed,
"Instances of weak management and lack of joint working within and across agencies remain in some areas," Ofsted said.
