The mythbuster guide for local authorities was withdrawn by the DfE in March after children's rights charity Article 39 mounted a High Court challenge over concerns it "removed important statutory safeguards" for children.
More than 50 voluntary organisations, academics and social work experts had called for it to be withdrawn.
At the time the judicial review application was made, the DfE said it decided to remove the guidance from circulation, rather than "divert time and public money to litigation".
Before the mythbuster guide was withdrawn, Article 39 submitted a complaint to the Information Commissioner when the DfE refused to release certain information including copies of previously withheld correspondence between department officials and local authorities in connection with the mythbusting document.
Article 39 also requested the names of public authorities and other contacts sent the innovation programme email pertaining to the mythbuster guide, and the job title of the official who sought agreement from DfE lawyers on the content of the document.
However, the DfE argued that, in light of the decision to withdraw the guide, it would be unfair to external partners that had previously contributed to or initially supported the guidance to disclose the information.
This information, the DfE said, if published, could potentially damage the professional reputation of some key stakeholders and deter them from engaging fully with the DfE in the future.
In a judgment published this week, the commissioner decided that the DfE correctly applied the law and the public interest favours withholding the information. The commissioner also found in favour of the DfE in relation to information from the emails was correctly withheld.
It was also noted that it is not generally the DfE's policy to make public the names of junior officials and the commissioner therefore accepted that the expectation from these individuals will be that their identity will remain private unless they consent to disclosure.
Carolyne Willow, director of Article 39, said: "It is significant that after the first welcoming tweet by the chief social worker for children and families [Isabelle Trowler], only one or two individuals within the children's sector came to the defence of the ‘mythbusting' guide. But this decision notice shows there were public officials within the Partners in Practice local authorities and central government who backed the document, and the Department for Education now concedes their professional reputations could be damaged should their identities and views at the time be made public.
"The implication is that nobody involved in those email exchanges raised the alarm and spotted that this was another backdoor attempt to deregulate and disrupt the statutory framework of children's social care. That's incredibly worrying.
"A freedom of information request to Ofsted revealed that it had deep concerns about the document's accuracy ahead of the publication and communicated these to the Department for Education. We applaud Ofsted's transparency and the fact that it identified the risks to children and young people.
"It's remarkable that a junior official was handed the task of seeking legal approval of the guide ahead of publication. We only sought the job title of this individual, and we're very surprised the Information Commissioner has supported secrecy over that."
The mythbuster guide was produced by the DfE's Children's Social Care Innovation Programme, with the aim of, according to ministers, clarifying misunderstood statutory guidance.
However, campaigners said it featured numerous errors and misrepresentations of the statutory framework on how social workers should support children in care. For example, the guide suggested it is acceptable for local authorities to provide one social worker for children and foster carers when a child is in a stable, long-term placement, when statutory guidance indicates there should be two.
Article 39 is currently considering whether to appeal the Information Commissioner's decision to a tribunal.
The DfE declined to comment.