Women primary teachers are working longer hours for no extra pay because they lack the bargaining power of male colleagues based mainly in secondary schools.
So says the Professional Association of Teachers which also claims that primary staff are expected to take on more duties than secondary teachers. PAT has 35,000 members - a large proportion of whom are female primary school teachers.
It was reacting to a pay survey by the School Teachers' Review Body, which showed fewer than one in two primary teachers got paid for extra responsibilities, in contrast with two in three secondary teachers.
One in two women teachers received such payments compared with two-thirds of male teachers.
PAT wants to see a new pay structure, under which all competent teachers take on extra responsibility together with higher pay achieving a "chartered teacher" status after five years.
Alan Manasseh, PAT senior professional officer, said: "Secondary teachers have more bargaining power because of the more hierarchical structures in secondary schools. Primary teachers frequently take on responsibilities without more money. By and large they accept it."
Mr Manasseh said: "Undoubtedly, there are thousands of primary teachers out there with responsibility for large curriculum areas - let's say science or a raft of humanities subjects - who will be paid less than a teacher in a secondary school responsible for a single subject. That's unfair."
The National Association of Head Teachers, while agreeing that primary and women teachers currently get a raw deal, does not think the solution lies in creating a new category of teacher.
David Hart, its general secretary, said: "The answer is to ensure that all teachers have a fair crack of the whip when it comes to distributing the pound;1 billion the Government has put on the table for the next two years." "Chartered teacher" status would simply complicate the complex process of devising a new salary structure following Green Paper plans to restructure the profession, he added.