The children's services department was described as "totally broken"
The lessons of the Edlington torture case will never be learnt unless the Serious Case Review (SCR) is published, the Conservatives have claimed.
They stepped up pressure on Children's Secretary Ed Balls to accept the need for "openness" and reveal the results.
But Prime Minister Gordon Brown has said publishing the full results of investigations into the handling of the case may identify vulnerable children.
Two brothers were detained indefinitely this week for the attack on two boys.
'Secrecy served no-one'
The case involved "prolonged sadistic violence" and sexual humiliation by the 10 and 11-year-old brothers on their victims, aged nine and 11. They must serve a minimum of five years.
Shadow children's secretary Michael Gove claimed the case could have been prevented if SCRs on previous child cruelty cases had been published in full.
The local safeguarding children's board published an executive summary of the investigation into officials' handling of the case, with most of the details removed.
Mr Gove said: "We know, from what has now been reported, that the Edlington tragedy was preventable if only children's services had been operating properly.
"If those SCRs had been fully in the public domain, then the council would have been held more accountable and the pressure to make real improvements would have been greater. Secrecy has served no-one."
He said lessons would not be learned unless the government accepted the need for "transparency, accountability, openness and candour".
He said the executive summary was a "wholly inadequate document" and simple editing of the SCR would be enough to safeguard children's identities.
Michael Gove described the executive summary as "wholly inadequate"
At prime minister's questions in the Commons on Wednesday, Tory leader David Cameron argued that the release of summaries in cruelty cases like Baby Peter had led to inaction.
But the prime minister said that publishing SCRs might inhibit the frankness of those involved.
Last week Mr Brown and Mr Balls said children's charity the NSPCC also believed SCRs should remain secret, but Mr Gove said its position had since "evolved" and it now recognised how inadequate many summaries had been.
The charity said it had reviewed its position and concluded that "the case for greater accountability within the child protection system is a compelling one".
It called for a system of quality checks on SCRs to ensure summaries were "an accurate distillation of the full report" so the public could see what went wrong.
But it said it still did not support the publication of full SCRs and sensitive information must be kept confidential to "protect vulnerable children".
A Department for Children Schools and Families spokesperson said SCRs are not published in full on the advice of Lord Laming and children's groups.
The spokesperson added: "It is for Ofsted, the independent inspectors, to assess the quality of SCRs and their summaries so they are completed to a sufficiently high standard."
Meanwhile, Labour MPs have criticised Mr Cameron for linking the Edlington case to his campaign claim that Britain is a "broken" society.
On his blog, former deputy prime minister John Prescott said Mr Cameron had attempted to twist a well-reported tragic incident to his political advantage.
He said: "This was a really sad case and I can't begin to excuse the actions of these kids. But to highlight it as an example of Cameron's much beloved 'broken Britain' is offensive, patronising and just plain wrong."