Former Ofsted boss Chris Woodhead has denounced the schools inspection body as an "irrelevance" and "a waste of public money".
The former chief inspector of schools told The Economist that Ofsted contributed very little to schools' understanding of their task and has become "part of the problem" in the education system.
Mr Woodhead, who led Ofsted from 1994 to 2000, also criticised the education policies of both the Labour Government and the Conservative opposition.
Discussing Ofsted's role, he told The Economist: "It is an exercise driven by the analysis of the data, and as such I think contributes very little to a school's understanding of what it's doing.
"It has become part of the problem in another, perhaps more sinister, way. It has become an agent of state enforcement.
"Ofsted inspectors are meant to comment on schools' contribution to 'community cohesion'. These are distractions from what teachers in schools should be doing. Ofsted is focusing on them. Therefore Ofsted is part of the problem."
Mr Woodhead said the Government had "no respect for the teaching of traditional subject knowledge".
But he accused the Tories of wanting to "have it both ways" by supporting a Swedish-style system of independent schools founded by parents' groups and voluntary organisations within the state system while at the same supporting the retention of the national curriculum.
He said: "You either plump for market-driven schools or you plump for the State telling schools what to do."
