It would be a negligence lawyer - preferably a lawyer who deals with NHS negligence.
The NHS Constitution says "you have the right to receive care & treatment that is appropriate to you, meets your needs & reflects your preferences",
Patients or their families have the right to compensation where they have been harmed by negligent treatment.
Patients can also exert pressure by referring the matter to their local Healthwatch - who are patient’s consumer champions - yours can be found here: https://www.healthwatch.co.uk ) / to the local press / to your local MP.
A complaint against social services is possible - and if that does not work then you can use the Ombudsman service. Which is free to use and quicker than court action. The Ombudsman's decision is binding upon social services if you also accept the decision.
It is the normal way to resolve such disputes - you must first go through the complaints procedure with social services. The Ombudsman will not take on your case unless you exhaust the complaints procedure first of all. The Ombudsman will accept the complaint if you have been directly affected by the matter and if you raise this within 12 months of becoming aware of the matter.
You will need the final response from social services, following your complaint.
Once you have that, you then need to register your complaint with the Social Care Ombudsman and you can do that here: https://complaints.lgo.org.uk/complaint-form/
If you disagree with the Ombudsman's decision, court action is then possible though is considered a "last resort".
You will generally need a lawyer for this stage of the dispute considering the complexities and potential costs involved (some may offer a no win no fee agreement so you pay nothing to them and are fully protected from costs if you lose).
Here are a few law firms you could approach :