An independent regulator, needs powers to define online platforms within the law, identify areas of concern, compel them to provide information and oversee the actions they take.
A regulator must have sharp teeth, starting with strong information gathering powers, the power to initiate enquiries, and the ability to impose effective sanctions including the ability to fine for non-compliance.
Purely voluntary approaches have failed. The issues are too big and far too serious. We as a society must find effective ways to stem the flow of hate, abuse, and offensive, illegitimate, and even dangerous content online.