When chancellor George Osborne announced in November that he was considering introducing regionalised pay for teachers, the reaction from the teaching unions south of the border was hostile in the extreme.
Now education secretary Michael Gove is set to reignite their fury by directly asking the private sector to advise on his plans to link teachers' pay with living costs in different parts of the country.
Most worryingly for the profession, the government is calling for evidence from businesses that have experienced "difficulty in recruiting or retaining staff" as a result of national pay deals for teachers. The British Chambers of Commerce says that the current system has created an unfair "labour market distortion", with firms in less prosperous regions unable to match salaries on offer in the public sector.
While business leaders feel that regionalising public-sector pay would allow them to compete with schools on a more equitable footing, teaching unions have warned that such a move could create a recruitment crisis in less prosperous regions.
"Regionalised pay is the next big threat facing teachers," said NUT deputy general secretary Kevin Courtney. "Taking money out of regional economies will really damage them. A job's a job; all teachers should be paid equally to do that job. We can't rule out industrial action over this issue."
Members of the School Teachers' Review Body (STRB) - the organisation Mr Gove is legally obliged to consult if he wants to alter teachers' conditions of employment - have yet to receive their remit letter, which will outline the kind of changes he is looking to make.
But rather than issuing the formal letter and then inviting responses from the statutory consultees - including the teaching unions and the National Governors' Association - the government has taken the unprecedented step of first inviting feedback from the world of business. A consultation letter issued by the Office of Manpower Economics asks for advice from the private sector on what criteria businesses use to set pay in different parts of the country.
Dr Adam Marshall, director of policy and external affairs at the British Chambers of Commerce, said the "labour market distortion" was created by a national pay structure that allows schools in rural areas to offer higher salaries than local business. "The evidence we get is that a lot of promising people who could come into a private-sector job end up in a public-sector job because of the existence of national pay scales."
At present, the only part of the country in which teachers are paid differently is the London area. Teachers in inner London on the bottom rung of the main pay scale earn almost pound;5,500 a year more than their counterparts in the provinces, to help them meet the higher living costs in the capital.
The trade unions fear that the move is politically motivated. With the expansion of the academies programme eroding the importance of national pay negotiations - historically one of the main ways they exert power over government - switching to a more localised system would see unions' influence continue to wane.
"Ministers are ideologically hell-bent on breaking up the teachers' national pay structure," NASUWT general secretary Chris Keates said.
Main pay scale
Rest of England and Wales
Upper pay scale
Rest of England and Wales