Investigatory Powers Bill

If there is a matter of acute public concern and a whistleblower is making himself a real nuisance to the Government, and communicates that to his Member of Parliament, should one member of the Government, the Home Secretary, ultimately authorise it, with it then being referred to the Prime Minister, who might also be affected by the decision? He would effectively be judge in his own court and surely it is at least arguable that some other scrutiny should be involved.