Mikus was last year convicted of the 1987 rape and murder of six-year-old Napier girl Teresa Cormack.
He was given a life sentence for Teresa's killing. Justice Gendall had no choice but impose a minimum non-parole period of seven years, the time available under legislation when the crimes were committed. He said Mikus should never be released.
After Mikus' conviction, CYF announced it had reopened its investigation into five historical cases involving 11 children who had had contact with Mikus since 1986.
Ms Pakura said Mikus was a sexual predator.
"Over a 20-year period when he wasn't in prison he was a transient moving from town to town and family to family.
"Some of his alleged victims were so young that it was difficult for authorities to gather evidence from them to withstand the tests needed for conviction."
She said Mikus was in control of himself and his circumstances and this was what enabled him to get away with so much offending for so long.
It was revealed after Mikus' conviction last year that he was sentenced for the attempted rape of a 14-year-old schoolgirl in 1983, while his son was in his house.
Despite his son's presence, Mikus was allowed to have custody of children with the knowledge of child welfare authorities right up until his arrest last year.
Mikus was a client of the department himself for both custody and sexual offending issues until he was 17.
Ms Pakura said CYF's first responsibility was to manage the cases of children who had had significant involvement with Mikus.
It included providing access to counselling and health services.
She called for the development of training, policies and practices relating to likely abuse cases.
She also said CYF's information systems needed to be improved.
"In the circumstances where social workers encountered Mikus... the department did not perform as well as it should have," Ms Pakura said.
"Looking ahead, I am confident that if there are improvements in policies, practices, systems and competencies as outlined, the department will be able to reduce the impact of other serial sex offenders on families and children."
Ms Pivac said the report highlighted a number of concerns for the department.
"Work is already under way to implement policy and training mechanisms that will enable staff to be better equipped to profile sex offenders, be alert to client safety in relation to sex offenders and be able to investigate and assess notifications where such offenders are involved.
- NZPA
Shannon Pakura, Chief Social Worker, CYF:
Appendix: Action Plan
Herald Feature: Child Abuse
Related links