Sir Michael Wilshaw, the new Ofsted chief inspector, has admitted he plans to scrap the satisfactory rating - a move which is predicted to shift many schools into special measures.

Up to 1,000 outstanding schools could also find their status under review where teaching is not at the highest grade. Chris Keates, general secretary of the NASUWT teaching union, has attacked the controversial speech:

"His statements today, after barely a month in post, now call into question every Ofsted judgment which has ever been made on any school ...This is puerile game-playing at the expense of schools, their teachers and pupils."

Shadow education secretary Stephen Twigg, however has defended proposed tightening up: "I'm glad that the Government appears to have performed a partial U-turn on inspecting outstanding schools. A rigorous Ofsted rating can't be a one-off occurrence."