The Ofsted boss has come under fire from two separate teaching unions, with one calling for his resignation and the other demanding significant changes to the inspectorate.
The National Union of Teachers (NUT) called for Sir Michael Wilshaw to resign, over claims he is demoralising teachers.
Delegates heard claims Ofsted was not an inspectorate but a politically-motivated "surveillance operation".
Roy Bowser, a delegate from Barnsley, said: "Mr Wilshaw you are Big Brother."
Mr Bowser accused Sir Michael of behaving like the education secretary's "junior minister" who oversaw an inspection regime that was "intrusive and invasive".
And the NASUWT union's conference in Bournemouth called for changes to Ofsted or, if that fails, a campaign for its abolition.
As chief inspector Sir Michael has cut the categories schools are rated by, scrapping the "satisfactory" rating saying all schools that pass their inspection should be rated as "good" or "outstanding".
He has also called for a sharper focus on teaching, saying schools should only be given the highest rating - outstanding - if they are ranked outstanding for teaching.
An Ofsted spokeswoman said: "Sir Michael has said from the outset any provision that is less than good is not acceptable.
"That's a tough message, especially for those schools and colleges that have been coasting. It's inevitable that when you challenge the system to do better, you will get some pushback."
She said the inspectorate had a new regional structure which gave "support as well as challenge" for schools and promoted improvement.
Both unions are in dispute with ministers over pay, pensions and workload, with fresh strikes expected in the summer.
The NUT's conference, in Liverpool, will later debate a motion of no-confidence in Michael Gove, the Education Secretary.
Delegates also called on the union to find legal ways that would allow teachers to boycott inspections, and voted to continue to campaign for Ofsted's abolition.
But some claimed this wasn't credible, and that any attempt to boycott inspections would be illegal.
Simon Horne, from Haringey, said this was "grandstanding" which would create "cheap headlines, but an expensive failure".
Earlier the general secretary of the NASUWT Chris Keates said teachers understood the need for inspection, but believed it had become too "high stakes" because a bad Ofsted rating could lead to a school being taken over or turned into an academy.
He said: "It's creating a climate of fear in schools and doing nothing to raise school standards."
A spokesman for the Department for Education said the academies programme was "turning around hundreds of underperforming schools and introducing a "world class curriculum".
The NASUWT has published a survey of nearly 3,000 of its members, which found nearly all (95%) said the school inspection system operated "in the interests of politicians rather than the public or pupils".
And 80% said they agreed the current model of school inspection "unfairly undermines public confidence in the education system".
The survey was carried out online by the union last month.