The chief inspector of schools in England said he has been left "spitting blood" over right-wing attacks from Michael Gove's Department for Education.
Sir Michael Wilshaw said he was "displeased, shocked, angry and outraged" by what he claimed were attempts from the Government to brief against the school inspection body Ofsted.
"I am spitting blood over this and I want it to stop," he said in an interview with the Sunday Times.
Sir Michael reportedly angered Mr Gove's administration by insisting upon using the same Ofsted standards for free schools and academies as inspectors do with any other school.
The right-wing think-tank Civitas has since urged the Government to set up a separate body to take over inspections for these schools, which are key elements of the Conservative Party's flagship initiative on education.
At the same time, the think-tank Policy Exchange, set up by Mr Gove in 2002, has asked schools to provide them with evidence on whether or not Ofsted is still "fit for purpose".
Asked whether he though it was time the Education Minister "called off the attack dogs", Sir Michael said: "Absolutely, it does nothing for his drive or our drive to raise standards in schools.
"I was never intimidated as a headteacher and I do not intend to be intimidated as a chief inspector."
He added that he had received "unjust" criticism from both the left and the right since Mr Gove appointed him to the post in 2011.
He also insisted that Ofsted would not be frightened into softening its inspections on free schools.
Recent inspections on free schools have led to the closure of Discovery New School, in West Sussex, while the troubled Al-Madinah school in Derby was labelled inadequate.
"If I see things going wrong in an academy chain I will say so," he told the newspaper.
"If people tied to the free-school movement think I will not do that they have another think coming.
"As long as as we exist and have the job of raising standards we will do the job fairly without fear or favour."
David Green, chief executive of Civitas, said: "The idea that Michael Gove is in any way directing our criticism of Ofsted is well wide of the mark.
"We have had serious misgivings about Ofsted for many years, driven by the testimony of teachers and their concern for school standards.
"The fact is, whatever Sir Michael Wilshaw's intentions, we know schools that would like to innovate are scared to do so because of the misguided notions of many Ofsted inspectors.
"It would not be in Michael Gove's power to 'call off' our criticism whether he wanted to or not."
Additional reporting by PAReuse content