If you are going to complain base your complaint around evidence. I looked at the councils children’s services policy and the social worker hadn’t followed loads of it and quoted sections. There are also a national framework they should meet:
Statutory guidance on the principles behind children’s social care, its purpose, factors enabling good practice and what it should achieve.
www.gov.uk
Statutory guidance on multi-agency working to help, protect and promote the welfare of children.
www.gov.uk
Have a read of these as they may help your complaint.