Increasing the frequency of inspections in struggling schools will drive away teachers and fail to raise standards, Ofsted has been warned.
Teachers' unions have rejected proposals to monitor underperforming schools up to three times a year. And the National Union of Teachers said the idea of giving high-achieving schools a six-year break between inspections - double the current three - would render the process "virtually meaningless".
The criticisms came in response to a wide-ranging consultation, which closed this week, on changes to the inspections process from September next year.
Christine Gilbert, the chief inspector, has proposed inspecting poorly performing schools more often, giving parents the power to trigger inspections, and setting exam results targets for schools in order to get a good inspection rating.
A proposal for no-notice inspections was dismissed by all unions as difficult to implement and indicative of a lack of trust in school staff.
Aspect, which represents most Ofsted inspectors, agreed. "Unannounced visits could prove problematic in terms of accessing what inspectors need; especially meetings with senior management," it said.
Launching the consultation three months ago, Ms Gilbert said that the changes were needed because school standards had "stalled".
She suggested that if schools did not hit a benchmark of 30 per cent of pupils gaining five good GCSEs, they should not receive an inspection rating above satisfactory. This plan predates the National Challenge scheme, which aims to have all schools hit the 30 per cent target by 2011 or risk being closed or taken over by high-performing schools.
But the NUT said returning to a system based on raw results would be "a retrograde step, which would have a devastating impact on the pupils and staff of schools serving disadvantaged communities".
The Association of School and College Leaders described the proposal as "grossly unfair to schools working in the most challenging contexts".
The unions also raised concerns about the proposal to give high-performing schools a "health check" every three years to make sure their performance had not slipped. They feared Ofsted would rely too heavily on test scores and contextual value-added marks.
"National data is not robust enough to be reliably used for individual school purposes, particularly for small schools," the Association of Teachers and Lecturers said.
"Year-on-year comparisons of school-level data are likely to be volatile, as one or two pupils in a cohort make an enormous difference to overall scores."
These concerns are likely to have increased following the Sats debacle this year, which called into question the quality of marking.
Ofsted's proposal to put more power in the hands of parents was also criticised. Chris Keates, of the NASUWT, said union members were "extremely concerned" about a system whereby people with an axe to grind might be able to trigger an inspection.