A pay increase, which thousands of teachers considered was so low it was worth striking over, could become even lower if the Treasury gets its way.
Ministers are asking teachers to accept a pay increase consistent with getting inflation down to 2 per cent. But cutting the agreed 2.3 per cent pay rise for 2009-11 is likely to prove too difficult for ministers, already struggling to avert a "summer of discontent" with strikes planned across the public sector.
The National Union of Teachers (NUT), which held a one-day national strike in April, warned that teachers would not accept further belt-tightening.
At a meeting this month, its leadership will discuss balloting for new industrial action in September. Support staff unions led by Unison have already agreed to strike on July 16 and 17, an action that threatens to close thousands of schools around the country.
The School Teachers' Review Body, the statutory group which advises the Government on teachers' pay, has not made a formal recommendation for 2009-11, but is due to do so in January.
Ed Balls, the Children, Schools and Families Secretary, has written to the group saying that the teachers' pay rise must be "responsible" and "affordable" and help the Government lower inflation to 2 per cent.
Mr Balls had previously agreed to a 2.45 per cent pay rise this year, and - under duress - to a new teachers' pay review for 2009 and 2010. He said in January that 2.3 per cent was the right pay rise for 2009 and 2010. But since then, retail price index inflation has hit 4.3 per cent, while food and fuel prices are rising even faster.
Mr Balls has warned that schools - many of which are getting a funding increase of only 2.1 per cent - cannot afford to increase teachers' pay by more than 2.3 per cent.
Barry Fawcett, head of pay for the NUT, said: "Teachers' pay has fallen considerably behind inflation and, at the very least, that needs to be remedied as soon as possible."
Martin Johnson, from the Association of Teachers and Lecturers (ATL), said below-inflation pay rises were unacceptable. ATL had no position on strike action, but he said members' stances were "hardening".