The Children's Ombudsman Dr Niall Muldoon claims young people have died by suicide because of the Government's 'inaction' on mental health.
He is extremely critical of the State's failure to put in place an initiative that was first suggested more than five years ago.
Dr Muldoon has written a detailed letter to Health Minister Simon Harris about the delay in implementing the Pathfinder Project for Youth Mental Health.
It has been released under the Freedom of Information Act.
He says the concept was first mooted in 2014, and would involve three Government departments working as a single unit.
Dr Muldoon claims the implications of not implementing it have been 'catastrophic' for the most vulnerable and at-risk children.
The Ombudsman clams that in that time, many thousands of children have languished on waiting lists for years - and been turned away from adolescent units.
Dr Muldoon says they have had to suffer the pain and anguish of being detained adult units.
He says he is in no doubt that we have ultimately lost children and young people to suicide because of the government's inaction around this project.
"By not making that happen, we continue with closed doors for children and families looking for help.
"We are in a situation where the Government are coming near the end of their time.
"This is one of their priorities for Government, but yet there's no action to be seen in bringing this unit into fruition".
In response, Minister Harris told Dr Muldoon that the Pathfinder initiative remains a priority - and that officials are currently looking into the legalities involved in setting it up.
Reporting by Eoghan Murphy