The Driver and Vehicle Agency in Northern Ireland has admitted to losing the personal details of over 6,000 drivers.
Two unencrypted discs sent to the Driver and Vehicle Licensing Agency (DVLA) in Swansea have gone missing in transit said the Northern Ireland agency.
The disks were sent last month to help with a safety recall by a number of car manufacturers. Details of 7,700 cars and the personal details of their 6,000-plus owners were sent.
No financial data is said to have been included on the disks. Replacement data to help with the safety recall was sent a second time on disk to the DVLA in Swansea, but this time it was delivered personally by DVA officers going there on other business.
The procedure of sending unencrypted disks in the postal system was established practice at the DVA, but was identified as a potential security threat in light of the massive HMRC breach, said the DVA.