The Yorkshire Post (p1) reports that the council's actions were specifically against the wishes of the boy's mother, who has since been in contact with two Doncaster councillors, who have helped her make a formal complaint against the social services department.
The father was convicted of serious sexual abuse against the boy when he was aged two. The boy was taken into care after his relationship with his mother broke down.
She said she had agreed to her son going into care on a temporary basis on the understanding he would be placed in foster care or residential care in the Doncaster area.
In a joint statement they said: 'Social services seems to have just washed their hands of the boy and put him at risk. This has to be investigasted as a matter of urgency.'
The complaint will be investigated by the Social Services Inspectorate. A spokeswoman for the Department of Health said no comment could be made on an individual case.