They will be unlikely to continue supporting the system if the School Teachers' Review Body does not recommend a compensatory pay award before the next pay deal for 200811.
The Government recently rejected a recommendation to reconsider the 2.5 per cent pay deal for 200607, despite average inflation being high enough to trigger it.
Ministers argue that the issue would be postponed until the review body's considerations of the next pay deal, for 200811. But unions say that would mean "there would be no confidence in the future operation of any trigger mechanism".
The National Union of Teachers says there is nothing to stop the review body making recommendations on pay before September 2008.
The Government has argued that inflation is due to come down as it is only being kept up by the temporary impact of oil prices. But the NUT believes this has lead to higher inflation elsewhere. The inflation rate on food was 5 per cent from March to May this year. The prospect of continuing turmoil in the Middle East, it says, will not improve the situation.
City analysts predict the retail price index, a standard indicator of inflation, will still be 3.8 per cent by September.
The NUT has argued that receiving a 2.5 per cent pay award two years in a row under these circumstances would mean teachers felt a "double whammy" in terms of recruitment, retention and morale. The submission added: "It is wrong, in principle and practice, for the Government to force low pay awards on public sector workers."
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said that teachers must not be treated like "Cinderellas" and warned their pay must not be allowed to return to the cycle of boom and bust it had experienced in previous decades.
The NUT also wants the review body to recommend that the upper pay scale for leadership becomes standard to promote pay equality.
Figures show that despite improved pay over the last 10 years, the gap between starting salaries for teachers and other graduate professions remain at around 12 per cent.
Unions are concerned that below-inflation pay increases will increase the gap.