The Ministry of Defence (MoD) has lost or had stolen more than 1,200 pieces of IT equipment capable of storing potentially sensitive data in the past two years - of which only 274 were encrypted.
The haul includes 342 laptops, 593 CDs, DVDs or floppy discs, 215 USB memory sticks, 96 hard-disc drives and 13 mobile phones.
The cost of the lost or stolen kit has been estimated at £620,000, according to a Freedom of Information (FoI) request submitted by PR consultancy Lewis Communications.
Only 25 of the laptops were recovered, and less than half of the devices were encrypted.
A government review of data-handling procedures - commissioned following the 2007 loss of two CDs containing 25 million child benefit records - introduced new measures that included mandatory encryption for data storage equipment.
But the FoI request also revealed that the MoD is not alone among government departments in losing equipment.
Eleven other departments reported losses totalling 518 laptops, 131 BlackBerrys/iPhones, 104 mobile devices and 932 memory devices, at an estimated cost to the taxpayer of £777,854.