A computer data disk containing the personal and financial details of around 2,000 members of the British Council has been lost.
The data lost includes names, national insurance numbers and salary and bank account details of the Council's UK staff.
The loss is the latest to embarass the government in recent months. The British Council, which is a Foreign Office-sponsored organisation, said the missing disk was securely encrypted to keep its contents safe.
The British Council said the disk was lost being transported from the organisation's payroll data supplier to its human resources department by courier firm TNT. It was a routine monthly delivery in December.
TNT is still looking for the disk. Security experts have asked why the government doesn't send data over secure networks, rather than vans.
A British Council spokesman said the system for transferring data is now being reviewed.