Controversial Ofsted chief Sir Michael Wilshaw has came under fire from headteachers who accused him of using negative tactics to raise school standards.
Delegates at the National Association of Head Teachers (NAHT) annual conference in Harrogate passed an emergency motion saying they are "saddened and dismayed" by his approach.
The move is likely to be seen as a highly personal attack on the Ofsted chief inspector who is himself a former school leader.
It also represents a further deterioration of relations between the union and Ofsted, and comes just days after the NAHT raised concerns over the variable quality of inspections and the watchdog's planned changes to the inspection system.
The motion, which was passed with a large majority, said: "This conference is both saddened and dismayed by the approach taken by the current HMCI (Her Majesty's Chief Inspector).
"We would encourage the use of language that creates a culture of support for schools and discourages negative rhetoric. We would expect HMCI to understand that to achieve the very best from teachers and children he needs to balance support with challenge."
It called on the NAHT's executive to use the Government's e-petition website to raise concerns about Ofsted's inspection system and seek a parliamentary debate on the issue.
Proposing the motion, Mike Curtis, an Oxfordshire headteacher, said: "Fear reigns and confidence wanes as Ofsted waves its stick! It is time to stand up to "bully-boy tactics."
An Ofsted spokeswoman said: "Ofsted has been listening to the views of headteachers, teachers and parents about its proposed changes to school inspections and will announce the results of its consultation at the end of the month. The intention is to work closely with good heads as they drive improvement in their schools."
NAHT members had yesterday considered a motion of no confidence in Sir Michael, but it was dropped after delegates raised concerns that the tone and wording was too strong.