Teachers' pay has fallen behind that of other professionals in both the public and private sectors, research for the National Union of Teachers (NUT) has claimed.
The findings have bolstered the case of those who are calling for nationwide strike action in a bid to avert seven consecutive years of below-inflation pay rises.
All the major teaching and support staff unions voted this week to "fully support" co-ordinated industrial action across the public sector in protest at the Treasury's 2 per cent pay cap.
The NUT has agreed to seek the consent of its 250,000 members for rolling strikes and stop-work meetings, starting in November.
"Yes, it is about declining pay levels for our members," said Christine Blower, the acting general secretary. "But it's also about making sure there are enough people coming into the profession to maintain the quality of our children's education."
Unison, which represents 200,000 teaching assistants and other support staff, already has a mandate to strike if this month's talks with local authorities collapse.
The research from Income Data Services, an independent pay consultancy, found that teachers did "consistently worse" than other professionals in four of the past six years. Of particular concern, given the shortage of science teachers, is that teachers' pay has fallen further behind that of scientists, engineers and doctors. Three years ago, teaching was the number one career choice for graduates, but since then it has dropped down the rankings.
The NUT, which commissioned the research, is demanding a big enough pay rise to wipe out five years of declining pay. Writing this week to the statutory School Teachers' Review Body, the union said a typical senior teacher had lost Pounds 3,954 in four years of below-inflation pay rises. Headteachers have lost far more.
The continuing decline in teachers' pay packets compared with other professionals is causing "real and sustained damage to the education service", the union said.
"It is a sad commentary in recent years that the world's fifth-richest country, which has consistently proclaimed the importance of education, has not chosen to protect its teaching force from what have been, by historical standards, relatively modest levels of inflation."
Teachers' pay increased by 2.45 per cent this month. But retail price index inflation hit 5 per cent - the highest level since July 1991. Fuel and food prices rose even faster.
The economic situation has worsened significantly since the NUT mounted a national one-day strike in April. This week, when union leaders met at the TUC in Brighton, the NUT was at the forefront of a hardline push for a general strike. In the end, they and other unions decided to support and co-ordinate local, regional and national industrial action in public sector pay disputes.
The NASUWT and the Association of Teachers and Lecturers have not balloted members for a national pay strike. But the NASUWT said its members would be taking local strike action over workload issues to support teacher assistants in other unions.
"We're not going to have our members victimised by the capitalist economic crisis," said Jerry Bartlett, the union's deputy general secretary.
Martin Johnson, ATL deputy general secretary, said the association supported the industrial action resolution because declining pay would make it harder and harder to recruit teachers.
"We listen to our members, and our members are becoming more and more unhappy with their pay situation," he said.
Keith Sonnet, Unison deputy general secretary, said the 2 per cent pay cap was an example of government "arrogance" from the days when Gordon Brown was still Chancellor of the Exchequer.
"Unless the Government changes its tack, there will be increasing industrial action, and it will have an effect at the next election," he said.