Barnet Council has been fined £70,000 after highly sensitive and confidential information on vulnerable young people was lost.

The data included the names, addresses, dates of birth and details of the sexual activities of 15 vulnerable children or young people. According to the Information Commissioner's Office (ICO), the loss occurred when a social worker took the paper records home to work on them out of hours; their home was burgled in April 2011 and a laptop bag, containing the records and an encrypted computer, was stolen.

The ICO's investigation found that the council failed to take appropriate organisational measures against the accidental loss of personal data held on paper records, and although the council had an information security policy and some guidance for staff on handling sensitive papers, these failed to explain how the information should be kept secure.

The council previously signed an undertaking in 2010 after data on 9,000 people was stolen in a burglary of an employee's home. The council avoided a monetary penalty as the loss was reported just before the ICO's powers came into force.

Although the undertaking introduced a paper-handling policy, this was not in place at the time of the second loss.

Simon Entwisle, the ICO's director of operations, said: “The potential for damage and distress in this case is obvious. It is therefore extremely disappointing the council had not put in place sufficient measures in time to avoid this second loss.

“While we are pleased that Barnet Council has now taken action to keep the personal data they use secure, it is vitally important that organisations have the correct guidance in place to keep sensitive paper records taken outside of the office safe. This includes storing papers containing sensitive information separately from laptops.”