Teachers' pay and conditions should be devolved to the Assembly government, according to an election pledge by Plaid Cymru.
Nerys Evans, the party's education spokeswoman, provoked a political row after saying that Plaid would seek power over pay and conditions if it wins the National Assembly elections in May.
Her comments, made at a hustings debate organised by teaching union ATL Cymru and chaired by TES Cymru, sparked angry comments from teachers and Plaid's coalition partners Labour.
Ms Evans said: "Plaid Cymru completely rejects the marketisation of education and the consequent erosion of pay and conditions.
"We believe the only way we can ensure the protection of our teachers' pay and conditions is for responsibility over them to be devolved to Wales before the Westminster government has the chance to erode them any further."
Teachers' pay and conditions are the only aspects of education not devolved to Wales, but the idea is unpopular with many in the profession who fear it could lead to their deterioration. Both the Conservatives and Liberal Democrats have ruled out the move.
Leighton Andrews, Labour's education minister, said Plaid's "shocking admission" put them at odds with the teaching profession.
"The implications of Plaid's proposal to undermine national pay-bargaining could lead to poorer pay and poorer conditions for teaching staff in Wales," he said.
"The First Minister and I have ruled out the devolution of pay and conditions for this very reason. We do not want to see an exodus of Wales's best teachers to England."
But Ms Evans said she was "stunned" by Labour's "admission" that pay and conditions would deteriorate if devolved.
Philip Dixon, director of ATL Cymru, said the biggest threat was from Westminster and the "localisation of pay" through the academies and free schools programmes.
But he said teachers would be left out of pocket if pay was devolved to Cardiff Bay.
"Given the track record of successive Assembly governments on school funding we suspect the temptation to raid the pot would be too great, and teachers would end up being paid less."
UCAC is currently the only teaching union supporting the devolution of pay and conditions.
Elaine Edwards, its general secretary, called for the establishment of an independent pay review body and a national negotiating structure involving all teaching unions.
She said: "We want to make sure teachers are paid a professional, fair wage for what they do, and at the moment that is being undermined by moves in Westminster.
"Pay and conditions should be devolved through a planned transition. We accept it's not going to happen overnight, but we have to plan for it."
A Welsh Labour spokesman said it was a point of principle, not an argument based on cost.
"The fact is that Wales has kept pace with England as far as teachers pay is concerned so the implication that we can't pay teachers properly is wrong.
"In fact, we have gone beyond what has happened in England by introducing, in 2006, pay parity between college lecturers and teachers."
Original headline: Labour fury as Plaid calls for devolved powers on teacher pay