The new format will be used for inspections across all settings, from early years to further education colleges, but will be tailored to the type of provider, Ofsted said.

Sir Martyn said the proposals were designed to “raise standards and improve the lives of children, particularly the most disadvantaged”.

He said the “suite of grades” would give parents “much more detail” and help identify a school’s strengths and areas for improvement.

But school leaders’ unions said the new system would add “enormous pressure” to schools, and could “worsen an already severe recruitment and retention crisis” in teaching.

Pepe Di’Iasio, general secretary of the Association of School and College Leaders, said the plans would generate a “new league table based on the sum of Ofsted judgements across at least 40 points of comparison”.

It would be “bewildering for teachers and leaders, never mind the parents whose choices these reports are supposedly intended to guide”, he added.

Paul Whiteman, general secretary of the National Association of Head Teachers, said the plans would “do little to reduce the enormous pressure school leaders are under”.

Daniel Kebede, general secretary of the National Education Union, said the five-point grading scale “maintains the current blunt, reductive approach that cannot capture the complexity of school life nor provide more meaningful information to parents”.

As well as criticism over its single-word judgements, Sir Martyn has also previously said Ofsted’s inspection process should be “far more empathetic”.

Those comments came in the wake of the inquest into Ruth Perry’s death, in which the coroner said the inspection at her school had “lacked fairness, respect and sensitivity” and was at times “rude and intimidating”.

Ofsted removed its practice of issuing overall grades for a school at the start of the current academic year, bringing in a temporary system of grading individual aspects of a school’s performance, ahead of the introduction of report cards in September.

Wirral head teacher Stuart Mycroft had his school, Castleway Primary, inspected under the current system in the autumn term.