Even the most moderate of the main classroom teaching unions may threaten industrial action to prevent a direct link between pay and pupil performance, it emerged.
The threat came as delegates prepared to gather for the annual assembly of the Association of Teachers and Lecturers, which opens in Harrogate today, and which Mr Blunkett is due to address on Tuesday. The Secretary of State will be aiming to calm teachers' fears, offering negotiations about details of the Government's proposals.
But the ATL general secretary, Peter Smith, is likely to tell the Government that it will need to concede far more before it can win teachers over.
While stressing his union's wish to deal constructively with the Government, Mr Smith is expected to warn Mr Blunkett to proceed with caution.
A senior ATL source said. "The feeling against what they are proposing is very strong. We would not be surprised if a resolution came up calling for industrial action, or at least non-cooperation with the new system of appraisal."
Mr Blunkett said yesterday: "What we are putting forward is a promise not a threat. It is a promise that if they are doing a good job in the classroom, they will be rewarded for it."