Pay and conditions consultant Nigel Middleton is so concerned about staffing reviews being rushed through that he has taken out an advert in The TES to publish an open letter to the Education Secretary Ruth Kelly.
David Hart, outgoing general secretary of the National Association of Head Teachers, predicted a "backlash" from his members.
He says they are running out of time to replace management allowances with new teaching and learning responsibility (TLR) payments because of a delay in the publication of guidance.
The pay plan, agreed between the Government, employers and the majority of teaching unions, means that all schools have to publish radical new staffing structures by the end of the year.
Mr Middleton, a director of the Head Support pay and conditions consultancy, said in his advert that this will be "impossible to do properly by Christmas". It concludes: "Our advice to Ruth Kelly: give schools an extra year to do the job properly."
Mr Middleton's consultancy has been running courses on the changes for headteachers and local authority officials because he believes they have had nowhere else to turn for information. He said demand is so high that he has had to take on extra staff.
He said heads were shocked and depressed when they realised what was expected, and that six heads had already told him that the prospect of staffing reviews in such a short time had been the "final straw" and had persuaded them to take early retirement.
He added: "We are short of headteachers already, and the last thing we want them all to do is leave. They really are demoralised about this. It is a recipe for unrest."
Mr Hart says the guidance, which the Government says will be published next month, is already overdue and should have been out as soon as the consultation period ended in mid-March.
Mr Middleton says next month will still be too late. With most schools holding only one staff meeting every week, he said they had "absolutely no hope" of having enough time for in-depth discussions with teachers about possible new structures, followed by a proper consultation on their final proposals.
He said: "If headteachers don't talk to staff first about these changes, then I believe they will have strike ballots."
Stephen Twigg, school standards minister, said he was working closely with the unions and employers and was confident they could make the system work.