UCAC, the Welsh-speaking teachers' union, has called on Welsh Assembly education and lifelong learning minister, Jane Davidson, to reconsider the membership of the school workload advisory panel because it includes "no one from rural areas, west Wales or Welsh-medium sectors".
The six-strong panel of three headteachers, a deputy, a teacher and a school secretary held its first meeting with unions in Cardiff this week.
John Hopkins, panel chair and president of the Secondary Heads Association Cymru, dismissed the criticism.
He said: "My school is nine miles from the Brecon Beacons and it serves rural villages. I don't believe there is a more rural secondary school than mine."
He admitted the panel lacked members from west Wales or from Welsh-medium schools, but said there had been few applicants from those areas.
Moelwen Gwyndaf, UCAC general secretary, insisted there were specific challenges facing small, rural and Welsh-medium schools which could be overlooked. For example, teachers in Welsh-medium schools often face extra work translating documents for parents who do not speak Welsh. Ms Gwyndaf has urged the Assembly government to appoint additional members.
She said: "We are particularly concerned because it has been suggested that no representatives of the right calibre could be found from these sectors."
An Assembly spokeswoman said: "Just over 40 people applied to become panel members. Given the number of applicants and the size of the panel, it would have been impossible to represent every school in Wales."
Meanwhile, Mr Hopkins said the panel had made progress during Tuesday's meeting and had identified some bureaucratic targets.
It hopes to abolish the statutory requirement for schools to provide an annual governors' report to parents.
It also wants to tackle the practice of setting GCSE targets three years before pupils sit their exams.
The panel was put together in September as part of last year's agreement to cut teachers' workload. Its remit is to advise on how bureaucracy can be reduced, but it has no powers to veto government policy.