Confidential files on 25 people were on a computer stolen from the home of a Kirklees Council employee.
The laptop theft was one of several incidents in which private data was lost by the authority.
The council also lost a paper file containing children’s social services information, it emerged in new details revealed by the authority.
But the worst case uncovered by a Freedom of Information request was the incident in which the laptop was stolen.
In all, 25 people had information lost including names, addresses and long term health needs in the theft at an employee’s home in March 2011.
Read more on The Huddersfield Daily Examiner