Health authorities have blamed a lack of funds for a rise of more than 600% in children and young people waiting too long for mental health services.
Government targets state no patient should wait longer than nine weeks for Child and Adolescent Mental Health Services (CAMHS).
Figures from Northern Ireland's Health and Social Care Board show 487 patients missed the CAMHS target in March 2019.
It was a six-fold increase from the 66 cases not seen in time in March 2018.
A statement from the Health and Social Care Board said CAMHS were "underfunded" across the UK and Northern Ireland staff had to work with "finite resources".
It added that its staff have been prioritising "emergency and urgent" cases and has established "crisis teams" in all five health trusts.
The waiting list figures, contained in the Health and Social Care Board Performance Report 2018/19, were highlighted by Ulster Unionist MLA Robbie Butler.
The report also shows that the number of adults waiting longer than the target time for mental health services has more than doubled over the year.
In March 2018, 648 adults had been on the list for more than nine weeks, but this rose to 1,529 in March 2019.
Mr Butler said he was seriously concerned by the "spiralling" waiting lists.
"Northern Ireland has the highest suicide rates throughout the UK, we also have by far the highest rates of poor mental health and yet we're the only UK region without a current mental health strategy," the MLA said.
"It is a scandal that as pressures are evidently building across our mental health services, the political impasse at Stormont is rumbling on."
In a statement to BBC New NI, a spokeswoman for the Health and Social Care Board (HSCB) said: "Across the UK, it is recognised that child and adolescent mental health services (CAMHS) are underfunded.
"Given the current pressures on services and finite resources, the Health and Social Care Board has prioritised several streams of work in this area.
"The HSCB has worked with all five trusts to establish crisis teams and improve access to emergency and urgent mental health care for children and young people.
"The Department of Health has recently confirmed additional investment of close to £1m from the Transformation Fund for CAMHS specific projects."
By April this year, 612 children and young people in Northern were waiting to access CAMHS.