Wales's teacher unions will not be given separate seats on the General Teaching Council for Wales (GTCW), after existing members voted against increasing its size.
The move has dismayed teachers' union the NASUWT Cymru, which has been campaigning for guaranteed union seats similar to those offered on the equivalent councils in England and Scotland.
It also criticised statistics showing that the 25-strong Welsh council currently has only eight active classroom teachers.
An overwhelming majority of council members voted against increasing the size of the GTCW, whether by ensuring seats for union representatives or by admitting more lay people to its numbers, at a meeting in Aberystwyth last week. Only three members opposed the move.
The GTCW is by far the smallest of the UK's four teaching councils, and its lack of numbers has been seen as both a benefit and a hindrance.
Education lawyer Ian Guy, who claimed that the guaranteeing of union seats on the council would prove problematic, said: "We are a useful, workable size, and I would be against expansion."
Other council members have disputed Mr Guy's view and called for increased numbers, professional or lay, to be added.
Fellow council member Tim Cox, a NASUWT national executive member, said:
"The council is definitely on the small side and I do not think we should worry about expanding it."
Geraint Davies, secretary of NASUWT Cymru, said afterwards: "We have said since the GTCW was established that the teaching unions of Wales should have a seat on the council, but turkeys never vote for Christmas.
"The profession should be properly represented on that council."