Fianna Fáil's spokesperson on Mental Health, James Browne, says Government funding needs to be managed carefully.
It was announced last October there would be additional funding of €55 million to improve local mental health teams for adults and children.
However, Fianna Fáil claims €25 million of that budget is being held back by the Department of Health.
Deputy Browne says the remaining money needs to be dealt with.
"It was with great fanfare that Budget 2019 announced additional funding of €55 million last October and I find it incredible that 11 months on so much of the funding is being held back," said Mr Browne.
He said that the HSE Service Plan for 2019 stated that the release of the money by the Department of Health was contingent on approval of implementation plans and commencement of specific developments.
"We all know that mental health services are hugely short staffed with Child and Adolescent Mental Health Services (CAMHS) having barely half the required number of staff in place," Deputy Browne said.
Why do Health Ministers announce funding without knowing if plans are in place to actually use it effectively?
He said that there is concern that the promised investment for 2019 will not happen.
"The fact is that demand for mental health services is not going to diminish and we need to see this money used to provide those services," he said.