More than 900 adults who were abused as children were referred to Tusla in the first four months of this year.
New figures show 38% of all 'retrospective abuse' cases have not been allocated a social worker by the agency.
Retrospective abuse is a term that refers to abuse an adult experienced as a child.
The figures show the Child and Family Agency got 176 of these referrals in April, bringing the total in the first four months of the year to 910.
In April, Tusla was dealing with a total of 1,481 retrospective abuse cases.
917 of these had been allocated a social worker, but 564 had not, including 56 'high priority' cases.
Minister of State at the Department of Children, Anne Rabbitte, has said the figures are unacceptable.
Minister Rabbitte said: "We know the damage for people who disclose and how traumatic it has been, and to think that they have not been allocated a worker has to be a priority for Tusla.
"In order to ensure that there isn't further wrongdoing being done and there isn't other families in the hands of other perpetrators.
"That these people who come forward, it has to be a priority."
Of the unallocated cases, the highest amount was in Waterford and Wexford, at 149.
Tusla said the number of retrospective abuse cases who have not been allocated a social worker is at its lowest in a year.