The underlying purpose of a regulator is to protect the public interest.
The duty of politicians is to make sure there is a regulator in place. Politicians also have a duty and a right to scrutinise the behaviour of regulators on behalf of the public.
When the Legislative and Regulatory Reform Act (2006) was consulted with regulators, 5 out of 7 welcomed it as they knew it would empower them in fulfilling their duties to a high standard.
Only Ofsted opposed it and they did this not only with the arguments which are recorded, there also seems to have been substantial obfuscation and a continual supply of misinformation. This is consistent with my personal experience of trying to engage in discussion with Ofsted.
Ofsted have shown no interest in adopting best practice in the interests of the public. They have instead chosen to be Gove's puppets for destruction - employing without complaint or objection procedures which is clearly established to be bad practice. The disproportionate level of punishment of schools which is taking place, the recategorisation of satisfactory as being unsatisfactory, the processes used by regulators to judge without forensic investigation, - these are all practices which other regulators cannot by law and would not wish to engage in.