More than 200 prison officers have received warnings about work absence in recent years, according to figures given to an Ulster Unionist Party MLA who claims it shows unfair treatment.
Doug Beattie alleged they “seem to be being targeted”.
He said in one case an officer had a warning overturned after it was recognised they were suffering from Post Traumatic Stress Disorder (PTSD).
The Department of Justice said the issue is “sensitive and challenging”.
Mr Beattie is being offered a meeting with the Northern Ireland Prison Service to discuss the situation.
The assembly member obtained a breakdown of written warnings issued in the past three years by the Department of Finance, which is responsible for employment issues involving officers as they are civil servants.
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Of a total of 349 warnings to civil servants, 203 related to prison officers, which Mr Beattie claims is disproportionately high.
“This is a pattern of discrimination which cannot be ignored by the Justice Minister Naomi Long,” he said.
A spokeswoman for her department said Mrs Long has taken “an active interest in the health and well-being of prison officers” and has already announced a review of help available.
There are about 1,200 prison officers in Northern Ireland.
Official statistics show they have the highest levels of long-term sick absence in the Northern Ireland civil service.
Mr Beattie said they perform “an incredibly stressful and dangerous role”.
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