By Gary Eason
BBC News, at the NUT conference
The biggest teachers' union in England and Wales is taking legal action against ministers over its exclusion from talks on working conditions.
Delegates cheered as Steve Sinnott announced the legal action
The National Union of Teachers says Education Secretary Alan Johnson misled Parliament about including "all the interested parties".
The row involves the Social Partnership involving the government and most education unions, but not the NUT.
Mr Johnson said he did not wish to comment in detail on the NUT's action.
The NUT has never belonged because it disagrees with provisions in the deal on reducing teachers' workloads that let classroom assistants - who are not qualified teachers - take lessons.
It also disagrees with the inclusion of performance-related pay in the recommendations of the independent body which advises ministers on teachers' conditions in England and Wales, the School Teachers Review Body.
The decision to seek judicial review of the government's actions was announced by the NUT general secretary, Steve Sinnott - to cheers from delegates at the end of his union's annual conference, in Harrogate.
Praise for the NASUWT
Shortly after Mr Sinnott spoke, Mr Johnson was praising the other big classroom union, the NASUWT, for its involvement in the Social Partnership.
At its annual conference, getting underway in Belfast, he said: "Trust and co-operation may be less stimulating than a state of permanent hostility, but it is certainly more rewarding for those who are strong enough and confident enough to engage.
"It is certainly no place for the weak and faint-hearted," he said.
Mr Sinnott told his members: "The NUT's exclusion from education policy matters is an outrage."
The review body had recommended a new statement on the role and responsibilities of teachers be drawn up "in discussion with all the interested parties", he said.
It had intended that this should include the NUT.
"Alan Johnson told the House of Commons that he accepted that recommendation. But he didn't mean it.
"He changed the recommendation. He would exclude the NUT as the NUT has been excluded since 2003."
Talking to journalists afterwards, Mr Sinnott said: "We think we have got a clear case here that the secretary of state has said one thing to Parliament and done another.
"That's wrong. He has misled Parliament."
The NUT has also reminded the government that the last time it took it to court, it won.
In 2000 the then education secretary David Blunkett was judged to have acted illegally over the introduction of performance-related pay for teachers in England and Wales.
The High Court said Mr Blunkett had improperly bypassed Parliament and the Welsh Assembly as well as the School Teachers Review Body.
Mr Johnson said he did not want to comment in detail on the NUT's action.
"They have written in terms of they are seeking a judicial review I believe and we are taking legal advice on that," he said.
"In terms of pay and conditions we consult with the NUT. They are part of the consultation process."