And a senior Office for Standards in Education official has admitted there has been a mixed response from headteachers and heavy use of the new grade 5, which assesses teachers as poor but does not warrant further action.

At the conference of the National Association of Inspectors Advisers and Consultants in Bristol this week, president Sheila Russell said she had received complaints from members that the new scheme, which grades teachers from 1 to 7, is unfair.

She said: “I cannot think of anything less designed to enhance the quality and effectiveness of inspections than the bureaucratic measures which quite inappropriately blunder into the headteacher’s proper role of knowing about and dealing with the competencies and capabilities of individual members of his or her staff.”

In a conference seminar Mike Tomlinson, director of inspections for OFSTED, admitted the new code of practice - which includes grading - did involve extra work for registered inspectors. He said OFSTED would review the code.

Early reports, he said, suggested that there has been heavy use by inspectors of grade 5. If a teacher gets a grade 6 or 7, inspectors must go back and monitor the teacher a second time.

Mrs Russell believes the ranking system must be changed. After the conference, she said the purpose of inspection was to report to the secretary of state and to schools themselves about standards and quality. “It is a lot to ask inspectors to also report on the quality of individual teachers as well. ”

Peter Miller, president of the Secondary Heads Association, said he thought the code was inequitable, especially for good teachers, and that could undermine the work being done by heads with their staff: “If a head has identified a member of staff as needing extra help and the inspection team does not pick them out and give them a poor grade, that can put us back.”

An OFSTED spokesman said the grades were meant to be used only as a guide for headteachers.