A sex abuse charity says it's worried sex offenders are continuing to pose a risk to children, even though concerns have been raised about them.

One in Four says it notified Tusla of 91 child abuse allegations last year, and 12 victims agreed to make full statements.

It claims eight of these allegations were either not investigated or were deemed "unfounded".

Three investigations are ongoing and only one case came back as "founded".

But it says only one sex offender is now being monitored.

One in Four executive director Maeve Lewis says this is very worrying.

"These are all people who have made very substantial allegations to us in the course of their therapy - and we would be very concerned as to why they're unfounded, why cases were not investigated.

"(There) may well be children who are at risk, even though the information has been given to Tusla".

In response Tusla says while it welcomes recognition of their positive joint working relationships in protecting children, it has denied the claim the agency did not investigate eight of the allegations brought to it.

Jim Gibson, chief operations officer, said: "Not all persons who have allegations made against them have criminal convictions for sex offences.

"Where a person makes and 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."