A number of children were left in the care of a foster family in the west of Ireland for several years, despite serious allegations of sexual abuse against one family member.

RTÉ's Investigations Unit has found that concerns first arose in 2007 when a young girl in respite care with the family alleged she had been abused by the then 18-year-old family member.

The same girl also claimed that a second girl, who had been living with the foster family for over a decade, had been abused by the same family member.

Inquires by the Health Service Executive found her disclosure to be "credible".

While both the HSE and gardaí investigated the allegations it was decided that two other foster children, one of whom was the long-term foster girl named by the initial complainant, should continue to stay there.

A care plan was put in place in which the alleged abuser was not to have unsupervised contact with them.

A file was sent to the Director of Public Prosecutions following the Garda investigation, but no prosecution followed.

It has emerged that four years later the girl named by the initial complainant also alleged she had suffered sexual abuse by the same family member.

Following that allegation the girl was removed from the foster home.

It was also decided that a third remaining foster child, a boy, should be removed but it was almost a full year before that happened.

On both occasions, in 2007 and 2011, the boy's birth mother was not informed of the alleged abuse until five months after the allegations were made.

Furthermore, despite the serious nature of the allegations and the decision to remove him, the boy was allowed to return to the family last year, at his own request, where he continued to receive part-time support up to recently.

The story follows last year's revelation that a young woman with profound intellectual disabilities was left in a foster home in the Waterford area for almost 20 years despite a succession of sexual abuse allegations.

During that period a total of 47 children were left with that family.

The story was the subject of several high profile hearings of the Public Accounts Committee before the dissolution of the last Dáil and it has resulted in calls for a statutory Commission of Investigation into the matter.