A disc containing nearly one million encrypted 999 call details was reported as missing last week.

The Scottish Ambulance Service claimed that the disc was lost by courier firm TNT en route to an IT supplier for use in the development of the service's command and control system.

The disc contained records of 894,629 calls to the Paisley Emergency Medical Dispatch Centre, and includes the names of patients, addresses of incidents and numbers received in calls to the centre since 2006.

However, the Scottish Ambulance Service has insisted there is little likelihood that the 999 details could be exposed as the encrypted disc was password protected.

"The information is encrypted and it would be extremely difficult to access any names or addresses," said Pauline Moore, acting chief executive of the Scottish Ambulance Service.

"It is disappointing and regrettable this has happened. We are currently addressing the issue with TNT."

Security experts have hit out at this latest public sector debacle surrounding compromised personal data.

"Despite assurances from the health secretary that the lost disc is fully encrypted and contains no private medical records, this loss is of huge concern to many people," said Brian Spector, general manager at security specialist Workshare.

"Unless the government is able to reassure the public that steps will be taken to prevent such an incident occurring again, confidence in its ability to protect sensitive data will hit an all time low."