Whitehall staff have been banned from removing laptops containing sensitive information from their offices after the Defence Secretary, Des Browne, admitted that two more computers had gone missing, following the loss of data from his department last week.
The Cabinet Secretary, Sir Gus O'Donnell, imposed the ban in an e-mail to civil servants which said: "Please ensure that this is communicated throughout your organisation."
Earlier, Mr Browne revealed that a Royal Navy laptop containing the personal information of thousands of potential recruits was stolen from a car in Manchester in 2006 and another was stolen from an Edinburgh careers office in 2005.
On Friday the Ministry of Defence admitted the details of 600,000 people had been stolen from a car in Birmingham on 9 January. Mr Browne told MPs the data was not encrypted.
Liam Fox, the shadow Defence Secretary, said 347 laptops had been stolen from the MoD since 2004 and there seemed to be a "systematic failure" in security.