Gillian Shephard, the Secretary of State for Education, will face protests from angry teachers when she addresses the biggest teachers' union today.
Left-wing groups are advising their members to sit in "stony silence" during the speech by Mrs Shephard, the first Secretary of State to speak to a National Union of Teachers' conference for 16 years.
The most militant delegates, including those who mobbed David Blunkett, Labour's education spokesman, last year, may walk out of the Cardiff conference.
Carole Regan, the incoming president, and a member of the "hard left", said she regretted the union executive decision to invite Mrs Shephard. "I don't think we should be inviting people who have destroyed education in the way the Government has done."
Teachers are furious about Mrs Shephard's decision to publish league tables for primary schools and to give into pressure from the Prime Minister for more grammar schools.
Mark Carlisle, the last Secretary of State for Education to address the conference, was booed off the platform.
Doug McAvoy, the union's general secretary, said the executive had invited Mrs Shephard, Mr Blunkett and Don Foster, the Liberal Democrats' education spokesman, to give them an opportunity to explain their views before the general election.
"It would demonstrate a weakness in the union to listen only to those it nearly agrees with," Mr McAvoy said.
Mrs Regan, a member of the socialist Teachers' Alliance, said she thought that "stony silence" was the best way to receive the Secretary of State. She urged Militant not to disrupt Mrs Shephard's 20-minute speech.
At last year's conference in Blackpool, protesters jostled and threatened Mr Blunkett and pinned him in a small room while they shouted slogans outside. None of the protesters have been expelled from the union and most are expected to be present this year.
Mrs Regan said: "I hope the people involved have learnt their lesson. They didn't get very much from it and were admonished by the majority of union members."
Mr McAvoy said Mrs Shephard could not expect a warm welcome, particularly after her U-turn on primary school league tables. He said: "I hope delegates will receive her in an appropriate way having regard to the fact that it is the NUT which is on show and not individual delegates."
He said he also hoped that Mr Blunkett, who will address the conference tomorrow would be received appropriately.
Splits between delegates and the leadership will surface again on Monday when the conference debates the executive's proposal to give all members a vote on important policy issues.
Local associations would have to ballot all members before sending motions to conference and conference decisions would have to be ratified by ballot.
At present, the conference is the union's policy-making body. Union leaders are proposing the changes after the left inflicted a series of defeats on the executive at last year's conference.
Conference motions calling for a one-day strike over class size and a special conference on salaries were overturned by a ballot of members.
Members have also been balloted on one-member-one-vote. Mr McAvoy said: "In every area members have voted to extend democracy in the way the executive have suggested. If conference rejects that, it will be rejecting the views of members."