Two more government laptops containing unencrypted personal details have gone missing, the Ministry of Defence has revealed.

The additional losses came to light during the investigation of the theft earlier this year of a laptop containing 600,000 peoples' personal details.

A Royal Navy laptop containing details of 500 people was stolen from a car in Manchester in October 2006 and a laptop was stolen from an army recruitment office in Edinburgh in December 2005, Defence Secretary Des Brown admitted.

"Our internal investigation has identified weaknesses in the application of MoD security procedures," Brown said.

The Ministry of Defence, which has launched a new inquiry in light of the two most recent laptop losses, does not appear to be the most careless government department.

One hundred and sixty nine Ministry of Justice laptops have been mislaid - lost, stolen or missing - since 2001, while the Ministry of Communities and Local Government has mislaid 28 laptops in the same period.

Departmental minister Parmjit Dhanda told MPs, "The official data on each of the laptops was not encrypted because none of the information was classified." In an attempt to reassure MPs, he added, "Each laptop was password protected."