According to the ICO, a systemic lack of staff training on how to handle personal information has led to the loss of sensitive personal information relating to thousands of children.
Sally-Anne Poole, the ICO's enforcement group manager, said that the three councils have shown a poor regard for the importance of protecting children's personal information.
It is, she said, essential that councils ensure the correct preventative safeguards are in place when storing and transferring personal information, especially when it concerns sensitive information relating to children.
"A lack of awareness and training in data protection requirements can lead to personal information falling into the wrong hands", she said.
The ICO says that theft from the home of an employee of the London Borough of Barnet was reported by the council. An unencrypted, non-password protected USB stick and CDs containing the sensitive personal information of over 9,000 children and members of their families were taken.
An employee had downloaded the data onto the unencrypted devices without any authorisation to do so, although it was later revealed that there was no training provided or security in place to prevent such downloads.
The ICO says it had conducted an audit of the London Borough of Barnet prior to this incident that had also highlighted this lack of staff training.
West Sussex County Council, meanwhile, had a laptop stolen, also from the home of an employee, which contained sensitive personal data relating to an unknown number of children and families involved in childcare proceedings.
The laptop was unencrypted and enquiries by the ICO revealed that the employee had not received any formal data protection/IT security training. It was also discovered that over 2,300 unencrypted laptops were likely to be still in use across the council's various services, although steps are now being taken to encrypt these.
Last, but not least, Buckinghamshire County Council provided a report regarding the loss, at Heathrow Airport, of documents containing sensitive personal data relating to two children.
The documents were in a plastic wallet belonging to a council social work employee who was travelling to another city in connection with the children's social care case.
After further analysis by the ICO, it was apparent that no real thought had been given to the security of this personal data during travel. It was also revealed that some of the council' policies needed revision and that staff training in data protection was insufficient.
As a result of these data security failures, the ICO has found all three councils to be in breach of the DPA.
All three government departments have signed formal undertakings to ensure staff will be made fully aware of the policies of their council for the storage and use of personal data.
The London Borough of Barnet and West Sussex County Council will also provide appropriate training on data protection and IT security and ensure portable and mobile devices used to store and transmit personal data are encrypted.
Sally-Anne Poole said that she was particularly concerned where a public authority has previously been warned about the lack of staff training in data security.
"Breaches involving such large numbers of children and family members could easily have been avoided. I am pleased that all of the councils have now taken or proposed action to prevent against further data breaches", she said.