A Teesside mother was not warned a man living in her home, who later raped her five-year-old daughter, was a known sex offender, a critical review has found.
Agencies on Teesside and in County Durham knew of the man's past, but did not share information which may have prevented the abuse, the report said.
Stockton Council has suspended a person and admitted a support worker visited the family, instead of a social worker.
The council, which compiled the review, has issued a "profound apology".
A serious case review found a catalogue of failings in the case, which happened in Stockton in 2008.
At the time of the assault, for which the man was later jailed for six years, he was receiving treatment and was being supervised by Cleveland Police and the National Probation Service Teesside and Durham.
His previous convictions were for three non-contact sexual offences against female children in County Durham, for which he received a 12-month suspended sentence.
The review, by Stockton's Local Safeguarding Children Board, said: "There were clear failures to consider the protection of [the child] and undertake a full assessment at the point agencies became aware of the original offending."
Jane Humphreys, who chairs the board, added: "Speaking on behalf of all the agencies we are profoundly sorry for our failures in this case.
"We particularly regret we did not provide the mother of this child with information to enable her to adequately protect her daughter. We are continuing to offer support to the family.
"The wellbeing of children is of utmost importance and we deeply regret the impact this case had on the child.
"The response was not satisfactory. We sent out an unqualified social worker, who failed to do an assessment properly.
"The mother was not given information in relation to the offences of the adult living in that household.
"We fully support the report's recommendations and will continue to work to address the shortcomings highlighted."
The report stressed the girl's family were not involved with any agency before the abuse took place.
In a statement, the girl's mother said: "Insufficient information was given to me to enable me to protect my daughter.
"I sincerely hope that lessons have been learned from this case."