The influence of the unions to shape Government policy on teachers' working conditions is in danger of being lost, the leader of the NASUWT has warned.
The status of the so-called Social Partnership - the key relationship between the Department for Education and teachers' leaders - is currently being reviewed.
Plans include involving a much wider range of organisations, including parents' and governors' groups. Ministers are also understood to be interested in giving the partnership a wider remit, including issues such as pupil behaviour, curriculum and assessment.
NASUWT general secretary Chris Keates said there was a danger that the partnership would "just become a talking shop", lacking real power.
"There have got to be rules of engagement," she said. "You can't have people sitting around the table who operate on different terms.
"The rules of engagement ensure the difference between people having a chat then nothing happening and what we have been able to deliver in terms of working conditions and raising standards."
The partnership had its first meeting under the new Government last week, attended by schools minister Nick Gibb. Before the election, the Conservatives refused to commit themselves to retaining the group's status as it had been under Labour.
It is understood that Ms Keates is unhappy at the prospect of the NUT being admitted to the Social Partnership.
The NUT refused to join it when it was formed because it disagreed with the 2003 workforce agreement, which guarantees teachers planning and preparation time. The National Association of Head Teachers (NAHT) is also excluded after refusing to sign an agreement on the roles of assistant heads.
The partnership in its current form is secretive: confidential discussions are held between unions, employers and the Government, and members then promote the decisions made.
The set-up has been criticised for reducing accountability and cutting ordinary union members out of key debates, but its supporters say it has achieved tangible improvements for teachers.
Mick Brookes, general secretary of the NAHT, said he hoped his union would return to the partnership under the new Education Secretary, Michael Gove.
"At the moment the partnership is not representative of the profession as two key unions are excluded," he said. "I would hope we will be able to take part in negotiating an arrangement without having to sell our souls."
The union has clashed with the partnership on several other occasions.
In 2005, it left after saying there was inadequate funding to promote teachers' rights to 10 per cent preparation and planning time.
Ms Keates added that she remained open-minded about developments in the partnership and had an attitude of "suck it and see".
Who's in the gang
- Social Partnership members:
- National Employers' Organisation for School Teachers
- Association of School and College Leaders
- Association of Teachers and Lecturers
- Unison (support staff union)
- Unite (support staff union)
- GMB (support staff union).