In one of the most expensive snubs in Irish political history, the secondary teachers' union ASTI has spent €35,000 holding a meeting to "dis-invite" the education minister from its annual conference.

Mary Coughlan, who is in the job less than a fortnight, has been told to stay away from the gathering, which starts in Galway on Tuesday.

The decision to bar the minister – originally targeted at her predecessor Batt O'Keeffe – came after a meeting of ASTI's 180-strong central executive council (CEC), which union sources estimate cost €35,000 to organise.

Unlike most other unions, which have around 20 people on their decision-making committees and can hold meetings in union premises, ASTI has to hire a hotel to hold its meetings. The union also covers the travel and overnight expenses of the delegates who come from all over the country.

Earlier this year, the CEC met and decided to break with the tradition whereby the education minister addresses the union's annual conference. The decision was made in protest at public sector pay cuts.

Since then, Tánaiste Mary Coughlan has replaced O'Keeffe, and the public sector unions and the government have hammered out a compromise agreement which gives some prospect of the pay cuts being rolled back over the next few years.

However, ASTI said last week the agreement was insufficient to re-invite Coughlan.

The Tánaiste will not have a completely free Easter week, however.

The primary teachers union INTO has invited her to address its conference on Tuesday morning, which takes place just down the road from the Asti conference in Salthill, Galway

The next day, the Tánaiste will head off to the TUI conference in Ennis, Co Clare, where she can expect a hostile reception from the militant union which, in keeping with tradition, has expressed its total opposition to the public service pay deal.