THE county's mental health service has admitted losing more than 8,000 patient records.
The Gloucestershire Partnership NHS Foundation Trust admitted the loss of 8,466 records at the weekend.
The partnership trust said health chiefs were told in November that a memory stick had gone missing.
Health bosses have reassured patients and said the information lost related to closed cases only and that there was no risk of unauthorised access to the archived files.
Shaun Clee, chief executive of Gloucestershire Partnership NHS Foundation Trust, said: "An immediate investigation has identified that this incident occurred due to a breach of policy. Lessons have been learned from this incident and appropriate actions have been taken.
"We are aware that this situation may cause some anxiety to patients. However, we would take this opportunity to reassure all patients that there is nothing contained on the memory stick that would pose any risk to them or their confidentiality and would again state that the confidentiality of clinical information is absolutely secure."
Geoffrey Clifton-Brown, Conservative MP for the Cotswolds, said: "Medical records are one of the most sensitive records held by government departments and it's absolutely vital that people who hold these records look after them carefully."
The trust was one of nine around the country to have lost patient records.
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