Teachers' unions have called for top-level discussions about the future of the General Teaching Council for Wales after the body changed its rules on disciplinary hearings without consultation.
The controversial revision will allow professional misconduct panels to call witnesses and examine written evidence - even if a teacher admits the allegations against them.
Last week, an extraordinary public war of words broke out between the council and the NASUWT over the rule change, with the union branding the council a "kangaroo court", and the council accusing the union of wanting to hide unprofessional behaviour by teachers.
But now several other Welsh teachers' unions have expressed serious concerns about the council's actions, with some calling for an urgent review of the way it operates and how it spends public money.
Rex Phillips, the NASUWT's Wales organiser, said the rule change "goes against the principles of natural justice and enables the public humiliation of teachers".
He accused the council of "grandstanding" and attacked it for changing its rules without any consultation.
Neil Foden, a north Wales head and executive member of the NUT, said it was "wholly inappropriate" that unions were not consulted.
"We have become increasingly concerned about the way the GTCW has operated," he said.
"It doesn't speak for the profession any more and there needs to be a discussion - a review - about the way it operates."
Philip Dixon, director of the Association of Teachers and Lecturers Cymru, called for a "serious discussion" about whether some hearings are in the public interest.
"We can't accept that the GTCW is the sole arbitrator of what's in the public interest," he said.
"Given that the GTCW's budget is stretched, I think it's time to ask about the cost benefits of this."
Dr Dixon said that teachers' unions, the Assembly government and other bodies, such as Governors Wales, should be involved.
Anna Brychan, director of the National Association of Head Teachers Cymru, said all parties could benefit from talks.
"There are some concerns about the way their (the GTCW's) processes work," she said.
"We are a little bit uneasy about this rule change and don't understand the thinking behind it."
Welsh-medium teachers' union UCAC said the council should consult unions before making changes to their procedures.
Elaine Edwards, its general secretary, said: "Open consultations would improve the process for all concerned and could avoid unnecessary disputes."
But Gary Brace, the council's chief executive, said the change was "minor and technical in nature" and it was not necessary to consult publicly on it.
"In discharging its legal responsibility for professional standards, it is necessary for the GTCW's hearings committee to fully understand the circumstances of a case so they can set appropriate sanctions," he said.
"Therefore, even when an offence is admitted, it may still be necessary for the key facts of the case to be presented."
The changes were reviewed and debated by the council for a year before being implemented, he said.
The NASUWT has stepped up its criticism of the GTCW over the past year since the council increased the mandatory registration fee for teachers by Pounds 12 to Pounds 45.
It recently called for the council to be merged with its English counterpart, saying it was no longer "fit for purpose."
The council came in for further criticism this week when new figures revealed that its hearings cost an average of Pounds 17,400, compared with just Pounds 9,800 in England.
The NUT attacked the council for holding hearings in luxury hotels in Cardiff, including the Mercure Holland House and Park Plaza.