Ofsted has admitted making a "serious and deeply regrettable error" in failing to disclose potential evidence in the High Court case of Sharon Shoesmith, the former Director of Children's Services for Haringey Council.
Ms Shoesmith is seeking a judicial review of the decision to dismiss her last year in the wake of the Baby Peter tragedy.
Last month the Guardian newspaper revealed documents showing that Ofsted downgraded an initial Annual Performance Assessment report into Haringey children's services from "good" to "inadequate" following the media coverage of the death of Baby Peter.
High Court Judge Mr Justice Foskett gave Ofsted 14 days to ensure no other documents in the case were withheld.
The latest disclosed documents include an inspector's notebook, various emails and drafts of the emerging report of the Haringey inspection in November 2008.
An Ofsted spokesperson said: "We very much regret that this has happened. We have apologised unreservedly to the court and other parties.
"Unfortunately mistakes sometimes happen and whilst this is a serious one and deeply regrettable, we have nothing to hide.
"Whilst we are very sorry for the late disclosure, we do not believe that the documentation we have disclosed today has any material bearing on the central issues in the case. We remain confident in the quality of the inspection and the findings in the report."