Heads, already warning the end-of-year deadline for reviewing staffing structures will be too tight, say unions are adding to the pressure by demanding that all the estimated 192,000 teachers on management allowances receive new teaching and learning responsibility payments (TLR).
The introduction of the payments, worth between pound;2,250-pound;11,000, from January is expected to mean thousands of teachers losing out because they are more focused on teaching and learning duties.
But The TES has seen advice from the three main classroom unions to heads in Croydon, London, saying all teachers on management allowances, worth between pound;1,638-pound;10,572, should receive the new payments.
It says no teacher should take on extra responsibilities without receiving one.
The advice contradicts that issued by the Rewards and Incentives Group (RIG) which is made up of Government, union and employer representatives.
It has agreed that there should not be a straightforward transfer between the two systems and that savings from the changeover will help fund experienced teachers' pay. David Hart, general secretary of the National Association of Head Teachers, has written to Ruth Kelly, Education Secretary, saying local NASUWT and Association of Teachers and Lecturers officials are openly briefing against deals signed by their leaders.
But the NASUWT, the second-biggest teaching union, denied the allegation and said its Croydon advice had been withdrawn. Meanwhile, the Assembly government is coming under pressure to delay the deadline for reviewing staffing structures in Wales to March.
Consultations on the regulations introducing the changes only finished yesterday. Draft guidance on carrying out staff reviews is expected before the summer holidays but is unlikely to be finalised until September.
Guidance for schools in England was issued at the end of May.
Gethin Lewis, secretary of the NUT Cymru, which is lobbying for more time, said: "The date of introducing TLRs would not change, but there would be more opportunity for consultation and guidance."
Nigel Middleton, a director of the Head Support pay and conditions consultancy, which has briefed 1,200 heads on the reviews, said: "There is going to be an explosion given the pressure heads are under from union reps. If the deadline is not extended by the autumn, I predict there will be a huge revolt."