Council bosses took legal action after a social worker mislaid a notebook containing sensitive information about families he was working with.
Bosses at Derby City Council discovered that Gideon Zeti's notebook had been read by a member of the public who had copied parts of it.
They feared that confidential information might leak out and persuaded a judge to grant an injunction barring publication.
Detail of the episode emerged in a ruling by a family court judge asked to make decisions in a case involving Mr Zeti.
Judge Clifford Bellamy said he had overseen a case involving a baby at a family court hearing in Derby.
He said Mr Zeti was the baby's allocated social worker.
The baby could not be identified.
Judge Bellamy said Mr Zeti had been at a meeting with the baby's parents in April.
He said Mr Zeti had left his notebook in the room where the meeting was taking place and had not realised until the following morning what he had done.
The judge said Mr Zeti had told how the notebook contained notes "detailing information that was confidential and sensitive" to families he worked with.
He said the notebook had been recovered, but council bosses learned it had fallen into the hands of a member of the public who had copied some of the information.
Bosses had taken legal action and Judge Bellamy said another judge had granted an injunction during separate legal proceedings in May.
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Rui Vieira / PA Wire.