National standards will be issued to heads and governors to help them assess teachers who have applied to move to the higher pay scale outlined in last week’s teaching Green Paper.

Ministers said the standards would not be prescriptive, and unions warned that if they were, and if they failed to win the profession’s support, chaos could ensue.

Under the proposed structure, classroom teachers who have hit the Pounds 22,410 ceiling can apply to move onto a scale of up to Pounds 35,000 in return for submitting themselves to rigorous appraisal followed by annual assessment.

The Government is to consult on the method of appraisal, but it proposes a mix of internal and external assessment which would include “a robust and careful assessment by the head of the quality of the teacher’s performance against the national standards”.

The Office for Standards in Education already has its own guidelines on good teaching and the Teacher Training Agency has also been working on a definition.

A spokesman for David Blunkett, the Education and Employment Secretary, said: “There will be national standards so head teachers have a clear idea what they should be looking for.”

The National Association of Schoolmasters Union of Women Teachers supported the principle of guidelines, saying it has had its own 16-point checklist for 20 years. But Nigel de Gruchy, general secretary, warned: “We don’t want it to be rigid and pejorative otherwise chaos will reign. It’s got to be sweet, simple and manageable.”

Doug McAvoy, general secretary of the National Union of Teachers, said: “If it doesn’t enter into the spirit of partnership with teachers then any of its reforms are in deep trouble.”