Education secretary Charles Clarke has snubbed one of the country's biggest teaching unions.

Clarke has rejected an invitation from the National Union of Teachers to address its annual conference this Easter.

For good measure his department announced that no minister will address the annual gathering.

The move follows the NUT's refusal to sign up to proposals for an enhanced role for classroom assistants.

The announcement brought a scathing response from the NUT's general secretary, Doug McAvoy, who described Clarke's decision as "immature".

"The government talks of partnership but is willing to practise partnership only with those who meekly agree with it," he said.

"The NUT has refused to sign up to an agreement which is flawed. It has done so because it disagrees with the government and the signatories on five key issues, issues on which the government has failed to respond.

"The NUT will put teachers and pupils first whether that means agreeing or disagreeing with the government."

Clarke hit back and issued a statement that listed the teaching union conferences his ministerial team would be going to.

The secretary of state, who in the past has been happy to trade on his reputation as a tough political operator, said the main reason for not going was that he had been expecting to get a rough ride from delegates.

"In recent years the conduct of delegates at the NUT conference has not encouraged a positive dialogue, indeed the opposite; and so the effect of the NUT conference has been to damage seriously the positive image of the teaching profession and teaching.

"I am not prepared to accept this way of working, and so no minister will attend this year's conference. The restrictions set out in the NUT's invitation make the possibility of constructive dialogue even less likely," he said.

"More generally, it is our intention to build new and more effective relationships with the teaching unions through our national agreement and the follow-up work we are doing together to implement it.

"The unions which have signed - both teaching and non-teaching - have shown leadership in the interests of their members, and of pupils. This is the way to engage constructively about school reform issues which have far-reaching implications and benefits.

"The refusal of the NUT to sign the agreement, which will reshape schools for the future, effectively reduces the influence of the union. I hope that members of the NUT, whose professionalism and dedication I greatly admire, will reconsider the decision which has been taken in their name."

Phil Willis, the Liberal Democrat education spokesman accused Clarke of running scared.

"It is no wonder the education secretary is scared of going to the NUT conference. He knows full well that it is teachers who bear the brunt of failures in our education system, particularly the failure to recruit and retain qualified staff," he said.

"Refusing to engage in debate with the UK's biggest teaching union is no way to reach sensible and practical policies for the benefit of our children's education."