The government has come under fire for failing to confirm what teachers will earn next year with just one month to go until the end of term.
Christine Blower, general secretary of the NUT, said it was "unacceptable" that teachers still do not know what they will be paid in 2009-10, and she urged ministers to clarify the situation. Her criticism came as Ed Balls said heads who permanently run more than one school should not have any cap imposed on what they can earn.
The Schools Secretary said this week he wanted to "incentivise" the best heads to lead federations of schools, and he rejected a recommendation that increases should be limited to 20 per cent above the top of the pay scale.
But he has refused to guarantee that a 2.3 per cent pay rise for all teachers, which was recommended earlier this year, will be honoured.
Mr Balls said he intended to implement the rise from September, but has reserved the right to change his mind in light of a further report from the School Teachers' Review Body (STRB), which recommends what teachers should be paid.
This latest report was submitted to Mr Balls earlier this month, but so far he has not published either the recommendations or his response to them.
"Ed Balls is reserving the right to alter the 2.3 per cent award after September 1 should the STRB recommend a lower pay increase," Ms Blower said.
"He has the STRB's report. He should publish it without delay, together with a confirmation that the promised 2.3 per cent will be honoured. It is unacceptable that teachers do not know for certain what they will be paid next year."
Martin Freedman, head of pay at the Association of Teachers and Lecturers, said he would have liked the Government to publish its final recommendations by now.
The decision on pay will need to be made as the public finances come under increasing strain because of the recession and ballooning levels of government debt.
One possibility is that the pay body will stick to its recommendation of 2.3 per cent for this year but cut another recommended rise of 2.3 per cent from September 2010 in view of the worsening economy.
A spokesman for the Department for Children, Schools and Families said teachers would receive a 2.3 per cent rise from September and that any changes to that award would be implemented later in the school year.
This creates the possibility of an unprecedented situation of teachers receiving a 2.3 per cent rise in September, which is then cut in subsequent months.
"The Secretary of State was crystal clear in his evidence to the review body that he considers 2.3 per cent remains appropriate," the spokesman said.
"He would need to be convinced of significant and material change in the economic and labour market conditions for there to be any change from the pay award for each of the next two years."
The final report and Mr Balls' response are expected to be published "shortly", according to the spokesman.
Ms Blower also questioned whether it was appropriate for limits on heads' pay to be removed.
"Headteachers must be properly paid, but we need to remember their salary comes from limited public funds," she said. "This is an area which needs careful consideration and we are calling for urgent discussions on that issue."