A group of employees from the Northern Ireland Public Service Alliance (Nipsa) union are in dispute with their employer over pay and job grading.
The grievance involves 12 higher executive officers (HEOs) at Nispa offices in Belfast and Londonderry.
In a statement, Nipsa said it was "committed to resolving this dispute".
Nipsa employees are not permitted to become members of the union they work for, but the staff involved are members of another trade union, Unite.
Unite representative Kevin Kelly said it was a long-standing dispute and he accused Nipsa's governing general council of a "failure to practice a standard of industrial relations that they would expect of their officials".
"My members are disgusted that their employer, who routinely challenges poor industrial relations practice across Northern Ireland, is acting in a manner which no employer would dare," Mr Kelly said.
"This dispute is resolvable if the will of the employer existed.
"It is therefore with reluctance and sadness that our members have been forced to take the ultimate action left open to them, that is the withdrawal of their labour".
The affected Nipsa employees are to hold a one-day strike on Friday 30 October and will then begin a work-to-rule protest from Monday 2 November.
Nipsa general secretary Brian Campfield said: "Nipsa is aware of the concerns of this group of its staff and has been involved in negotiations with their trade union, Unite, about how the issues in contention can be resolved to the satisfaction of both parties.
"Nipsa has advised Unite that it is committed to resolving this dispute and is presently engaged in further work which will hopefully settle any outstanding matters."
Trade union staff are to take strike action against their own organisation, claiming it has been "acting in a manner which no employer would dare".