The One in Four charity has said it is extremely worried that dangerous sex offenders may be continuing to abuse children, even though it has alerted the child and family agency Tusla to allegations against them.
The service has urged the Government to significantly improve the resourcing of the agency's child protection teams to enable them to deal with notifications nationwide.
One in Four professionally supports adults sexually abused in childhood and operates a sex offender intervention programme.
One in Four's 2016 annual report, published today, states that most of its child protection notifications to Tusla are deemed unfounded.
Last year, it sent Tusla 91 notifications based on what it calls clients' "very serious allegations ... about experiences of child sexual abuse".
Although 12 clients made full statements to social workers, the report says three of their cases were not investigated while five were deemed "unfounded" by Tusla.
The charity says the agency is still investigating three cases but that only one has been validated, meaning that only one of the many accused is now being monitored.
One in Four adds that in 79 of the 91 cases, clients chose not to meet a social worker and concedes that it is very difficult for Tusla to investigate without a full statement.
Responding to the One in Four report, Tusla Chief Operations Officer Jim Gibson said: "We acknowledge that One in Four made a significant number of notifications in 2016, and a small number of clients made full statements to Tusla however, we refute the assertion that we did not investigate eight allegations.
"Where a person makes an allegation and decides not to engage with social work staff regarding the assessment, Tusla staff proceed on the basis of the information available and follow through as appropriate.
"We cannot, however, compel people to make a disclosure against their wishes."
One in Four Executive Director Maeve Lewis has said the charity is extremely worried that dangerous sex offenders may be continuing to abuse children, despite the official notifications.
She warned that sex offenders generally continue to abuse until they are caught and that, although Tusla has made strides nationwide in putting in place teams to process retrospective allegations, One in Four's figures speak for themselves.
With next week's Budget approaching, she urged the Government to significantly improve the resourcing of Tusla's child protection teams to enable them to process notifications nationwide.
Speaking on RTÉ's Morning Ireland, Ms Lewis said: "I would really call on Katherine Zappone, the Minister for Children, to ensure in the Budget that sufficient resources are put in place."
Last year, 40% of the charity's 800 or so clients were male and it says this challenges the idea that boys are not sexually abused.
Almost half (46%) of those counselled said they were abused in their own families, with strangers accused in one-fifth (19%) of cases.
Catholic Church figures and friends and neighbours were each said to be responsible for one-tenth of abuse, while 9% were abused by more than one person.
The charity said that, despite suicide attempts being common among clients, over 60 people are awaiting a counselling appointment and its waiting list is closed.