One person has been sacked and two others have left South Gloucestershire Council after three serious breaches of data security by staff.
In one incident, a letter containing a foster child's address was disclosed to the birth mother, the council said.
The three breaches were among 198 data security incidents at the council last year, according to an annual report.
The council said it was working with staff to reduce the number of incidents to the "lowest level possible".
The three breaches by children's services staff involved sensitive personal details and were reported to the Information Commissioner's Office (ICO, according to the BBC's LDRS.
The second incident saw a council officer disclose to a father the identity of a neighbour who had reported concerns about his ability to look after his children.
In the third breach, sensitive personal data was included in a report and sent to the mother of a child who was thought to be at risk from that person.
No disciplinary action was taken after the foster child's address was disclosed "accidentally" because a council investigation found it was a "genuine one-off mistake due to a misunderstanding", a spokesperson said.
But the council revoked the employment contract of the officer who revealed to a father the identity of his complainant, and the two officers responsible for the third breach left after procedures to manage their performance were started.
Deputy council leader Jon Hunt, who is also the cabinet member for children and young people, said the "vast majority" of the incidents were down to "human error" by "very busy" staff.
"It's very simple errors that happen, and a lot of it is just typing the wrong email address in.
"But they're not usually significant data breaches and they're very easily rectified," he told the council's cabinet.