The Ministry of Defence has revealed that 121 of its USB memory sticks have been either lost or stolen since 2004.
Some of the memory sticks contained secret information, admitted the MoD. The MoD said it does not know when, where and how the memory sticks were lost.
The MoD has also revealed that more than 650 laptops have been stolen over the last four years, which is nearly double the figure previously thought.
Previously, the MoD had confirmed that 347 laptops had been stolen between 2004 and 2007.
Defence secretary Des Browne issued the revised laptop figures after "anomalies in the reporting process" were discovered.
The official total is now 658 laptops stolen, with a further 89 lost. He said 32 have been recovered.
The information on the lost or stolen memory sticks was received after a parliamentary question tabled by Liberal Democrat MP Sarah Teather.
It was disclosed that three of the memory sticks contained "secret" information and 19 carried "restricted" information.