“Who gets persecuted: the Local Authority? Social Services? The Foster Home? Foster Carers?”
Under section 17(1) of the Children and Young Peoples Act 1993 any person with parental responsibility for a child or with care of a child is automatically liable for a criminal offence under section 1(1) for not keeping the child safe from suffering the offence.
When a care order under section 31 Children Act 1989 is in force the local authority holds parental responsibility by virtue of section 33.
However, the police do not investigate the offence,
(see https://www.whatdotheyknow.com/request/police_child_cruelty_i#incoming-395351)
There are no prosecutions of officers, employees and agents of the local authority.
(see https://www.whatdotheyknow.com/request/prosecutions_for_child_cruelty_i_2#incoming-397023).
Alastair