Hundreds of medical records have been lost by hospitals here over the past four years, new figures have revealed.
Since 2012, nearly 350 incidents of records being lost or patient confidentiality being breached by health trusts have been reported to the Department of Health.
The figures, which emerged in an answer to an Assembly question to the Health Minister, have led to calls for action to be taken to protect confidentiality.
There were 346 incidents in total, the highest in 2014 when the number of cases rose to 108, dropping 12 months later to 69.
The minister's response did not reveal any detail of the type of losses in each trust area.
UUP health spokeswoman Jo-Anne Dobson, who asked the question, said that any loss or was a serious matter.
It has previously been revealed that in 2012 a client's referral details appeared on Facebook after a staff member dialled the wrong number and left a message on a machine.
Ms Dobson said the latest figures were concerning and that she was "deeply disturbed" by the volume of incidents.
"The problem has deteriorated significantly over recent years so it is essential that Simon Hamilton gets to grips with an issue which he was very vocal about himself as a backbench MLA in 2008 - a time when the number of reports going missing was comparatively lower compared to two or three times that now," she added.
"It is clear that minimum standards regarding the safe and secure handling of deeply private and confidential documents are not being met.
"The loss of a medical record can delay and impede the timely delivery of care, and as we all know, the longer the patient has to wait the more prospect there is of them coming to harm.
"I would call on the minister to take all necessary steps to ensure patient confidentiality right across the health service, wherever the records be held on paper or electronically, to restore patient confidence."
A DHSSPS spokeswoman said: "Each health and social care organisation is responsible, as data controllers under the Data Protection Act (DPA), for the management of records and personal information.
"They must ensure they comply with the DPA, and are answerable to the Information Commissioner for breaches of personal data."
Disciplinary action taken in cases of recorded incidents of lost or breached medical records is the responsibility of each individual organisation.