The Health Information and Quality Authority has criticised the Health Service Executive's fostering service in Dublin north central.
HIQA found that children remained in unsuitable and unsafe placements.
This HIQA inspection of the Dublin north central fostering service is a follow-up to an inspection report of July last year.
It criticises the HSE for failing to fully implement the 'Children First' guidelines and says some children continued to be at risk.
Children remained in unsuitable and unsafe placements and some were placed with unassessed and unapproved foster carers - a practice described as 'unacceptable’.
HIQA says there were cases where additional children were placed with some foster carers, against whom allegations had been made.
14 new complaints were made against foster carers since the original inspection report last year.
The HSE also failed to establish a national register of allegations.
HIQA says there was evidence of allegations of a similar nature, made about foster carers over a protracted period of time by different and unrelated children.
The HSE said this evening it is fully committed to implementing all of the recommendations of the HIQA report into foster care in Dublin North Central.
The executive said it would provide HIQA with updated action plans.