Social Services,how do they get away with it?

Im asking how the children's social service department get away with neglect of duty were kid's are often killed and/or maimed by adult's and yet unlike any other agency bar the police no one is ever jailed or even prosecuted.Yet time and time again they single out innocent(usually poor and unemployed)single parents.In many ways the social service's children's department are more sinister and closed to scrutiny than the police,can anyone answer as to why there has never(besides Cleveland)been a public enquiry into these people's often illegal and corrupt practices?