Surrey and Sussex Healthcare NHS Trust reported the breach to the Information Commissioner's Office (ICO) shortly after the unencrypted memory stick was lost late last year.

An ICO spokeswoman said: "After investigating the breach, the ICO warned the organisation that their policy covering the storage and use of personal data must be followed by staff and the trust must make sure their staff are appropriately trained on how to follow it.

"The trust was also warned that any repetition of such an incident may result in formal regulatory action." More