Ask your local childrens services for their complaints procedure as each one may differ slightly but as a general rule the following applies.
Stage 1 complaints-response in 10 working days from complaints manager.
Stage 2 complaints-response in 65 working days, independent investigator who does not work for the council will meet with you to discuss your complaint and will then interview all other persons/departments involved in your complaint.
Stage 3 complaints-response within a non timescaled time but usually within a month if not sooner, meeting with a stage 3 independent review panel, normally 3 persons and note taker.
Contact the complaints manager for childrens services, make bullet points of your complaint, ensure you have evidence to back up what you are saying (this is where names, dates and note taking come into play)
you can contact the ombusdsman if the complaint is taking longer than the timescales specified by the complaints manager (ask for a copy of their complaints procedure and timescales), the ombudsman cannot get involved but will give you a reference number to refer to for all future correspondence and can contact the complaints manager to hurry them up!
Contact your local MP, they are there for you so let them earn their keep!
If your complaint is about an individual social worker's fitness to practice contact their regulatory body-The Health and Care Professions Council
Social Workers must practice under the name they are registered under on the HCPC register, check their details and check the register if they do not appear then they are working outside of their registration requirements and this is misconduct as it is witholding public information which is illegal!
Tip-if you search the register and the name does not appear-search their surname-you can then scroll through the list to track down their work area and registration number-you will need the registration number to make a formal complaint.