The factory ceased operations at the end of May.
Bord na Móna is being accused of breaking the terms of the agreement entered over the closure of Derrinlough Briquette factory.
It's because the company has decided to put the site in Offaly up for sale without consultation with the unions.
SIPTU is making the accusation, claiming its "engaging in an act of industrial vandalism. "
Operations at the factory ceased at the end of May.
The union's divisional organiser, Adrian Kane says the sale shouldn't go ahead:
The sale of Derrinlough Briquette Factory can't go ahead until all the possibilities for the site are looked at.
That's according to SIPTU, which says Offaly County Council and the Midlands Regional Transition Team has to be consulted on future plans for the factory.
SIPTU's Divisional Organiser, Adrian Kane says he has one idea in mind:
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