Junior minister Cathy Ashton will speak at an NUT conference on special needs on Monday, marking what the union hopes is a thaw in relations after a series of snubs, following its refusal to sign the school workforce agreement.

Charles Clarke, Education Secretary, has refused to attend the union’s annual Easter conference for two years running.

John Bangs, NUT’s head of education, said he was “surprised and delighted” that Baroness Ashton had agreed to speak. “Whether or not this is a breakthrough we will have to wait and see,” he said.

A spokesman for the Department for Education and Skills said it did not work with the NUT as it does with signatories to the workforce deal, but there was no ban on contact. The union had been supportive of some of its SEN programmes, he said.

Elsewhere fall-out from the refusal to sign the deal continued when the leader of the trade union movement reprimanded the NUT for its behaviour towards other teacher unions.

Brendan Barber, Trades Union Congress general secretary, is understood to have accused the NUT’s national executive committee of damaging relations with the deal signatories through leaflets and adverts describing them as the “Governmen’s unions”.

“It was a ticking off and it was water off a duck’s back,” said one senior NUT figure. Neither the TUC or the union would officially comment on what they called a private meeting.

Martyn Powell-Davis, NUT Lewisham secretary, has stepped up his campaign to be general secretary by pledging to join the “awkward squad” if elected, working with other left-wing union leaders to take on the Government over public services. He is standing against Steve Sinnott, deputy general secretary, Mr Bangs and Ian Murch, West Yorkshire national executive member, in the June ballot to succeed Doug McAvoy.