Five local authorities have been found in breach of the Data Protection Act (DPA), leaving the Information Commissioner's Office (ICO) pleading for them do improve their security practices.
Basingstoke and Deane Borough Council managed to make four separate blunders in just two months in 2011, one of which saw data relating to 29 people living in supported housing sent to the wrong recipient.
At Brighton and Hove Council, an employee emailed the details of another member of staff's personnel data to 2,821 council workers.
Dacorum Borough Council, Bolton Council and Craven District Council were also caught out.
Failures not only put local residents' privacy at risk, but also mean that councils could be in line for a sizeable monetary penalty.
All have signed undertakings promising to shore up their data handling.
"At a time when councils are increasingly working with community partners, when data is shared it is vital that they uphold their legal responsibilities under the Data Protection Act. Failures not only put local residents' privacy at risk, but also mean that councils could be in line for a sizeable monetary penalty," said information commissioner Christopher Graham.
"We must also consider the detrimental impact these breaches continue to have on the individuals affected. Disclosing details about someone's social housing status can be upsetting and damaging for those affected."
Graham is currently looking to the Government to give it greater audit powers.
The ICO's announcement came just two weeks after Midlothian Council was handed a record fine of 140,000 after sensitive data relating to children and their carers was sent to the wrong recipient.
The ICO may get greater fining powers too if the UK adopts the European Commission's data protection regulation proposals.
