A £100,000 fine has been handed to Hampshire County Council after documents containing personal details of more than 100 people were found in a disused building.

The social care files, along with 45 bags of confidential waste, were discovered by the new owners of Town End House, in Havant, when it was purchased in August 2014, and contained highly sensitive information about adults and children in vulnerable circumstances.

Steve Eckersley, head of enforcement for the Information Commissioner's Office (ICO), which issued the fine, said: "Hampshire County Council failed to ensure that highly sensitive personal data about adults and children in vulnerable circumstances was disposed of.

"The council knew the building had housed a department that dealt with confidential information and should have had a proper procedure in place to check no personal data was left in the building. Organisations must implement effective contingency plans to protect personal data when decommissioning buildings.

"The council’s failure to look after this information was irresponsible. It not only broke the law but put vulnerable people at risk."

The ICO investigation found the council had failed to follow the law which says that organisations, be they businesses or public authorities, must have technical and organisational measures in place to guard against accidental loss or destruction of personal data.

The new owners bought Town End House after Hampshire County Council’s Adults and Children’s Services department left the building, meaning there were two years when agents selling the property and prospective buyers had access to it.

Mr Eckersley said: "Thank goodness the company reported the find of personal details. If the information had ended up in the wrong hands it could have had distressing consequences."

A spokeswoman for Hampshire County Council said: “We are very sorry that this incident occurred. Hampshire County Council takes the management and protection of its data very seriously. Accordingly, appropriate procedures were in place at the time, but unfortunately, on this occasion, the process was not fully adhered to. However, at no time was any information disclosed outside of the site.

“Immediate steps were taken to investigate the matter fully, and remedial action was taken. This has included strengthened and improved processes in the removal of, and destruction of, confidential waste from vacated buildings.

“We reported the incident to the ICO as soon as we became aware of it, which was at the point the company referred the incident to the county council – and have cooperated fully at all stages of the ICO’s investigation. We are currently considering the ICO’s decision.”