The BBC has been doing some digging:
Personal data about members of the public has been lost or wrongly revealed by 13 London councils in the last year, a BBC survey has found… In one instance, sensitive information about children in care was stolen when a youth worker took files into a bar.
This response is frankly irritating:
Tim Allen of the Local Government Association emphasised that data security was very important to local government
It’s demonstrably not important enough. There seems to be a second story here, too:
Some 23 councils replied to the freedom of information request
But there are 33 councils in London, all of them public authorities bound by the Freedom of Information Act. What happened to the other 10?
The ARCH Blog 
[…] If you’re wondering where you heard that before, it was last uttered a month ago by the LGA. […]