More than 3,000 working days were lost last year because of assaults on staff at the Oberstown detention centre for young offenders, it has emerged.

Figures from the Department of Children and Youth Affairs show that in the year from December 1st 2014 to November 30th last year, 65 employees were off work for a total of 3,005 working days due to assault and injury at Oberstown.

The North Dublin facility is the official National Children’s Detention Centre and caters for approximately 74 boys and six girls.

Incidents and assaults are graded at three levels and in the year under consideration, there were a total of 102 “incidents”.

One incident reported was at grade one level, the most serious, requiring emergency action and reporting to the facility director, the department and other emergency contacts at any hour of the day or night.

There were 46 incidents at the next critical level where the emergency services are called and the department is also informed and 55 incidents at the lowest grade three level.

These incidents are still "significant", according to Minister for Children James Reilly but "should not involve the emergency services, should not involve any serious injuries and should not involve any serious property damage".

In reply to a written parliamentary question from Sinn Féin health spokesman Caoimhghín Ó Caoláin, Dr Reilly reiterated that “any and all incidents resulting in assault and injury to staff or young people are to be condemned and there is no ‘acceptable’ level of assault or injury in a children’s detention school”.

The Minister told him that the risk of injury could not be excluded completely given the nature of a children detention school.

“The trend of incidents in this area, the level of supports available and the lessons learned from each incident are kept under ongoing review by campus management.”

Mr Ó Caoláin has repeatedly raised the issue of deteriorating safety for staff and young people in the facility and said the number of notifiable incidents was both alarming and unacceptable and had to be addressed without delay and satisfactorily.

“There is a compelling case for an urgent review of staffing numbers, training and support systems at the Oberstown facility. That 65 individual staff members were assaulted and so seriously assaulted, resulting in the loss of 3,000 working days over a 12-month period makes the case.”