The RTÉ Trade Union Group (TUG) has written to the Director General of the organisation accusing management of breaching policy in relation to a recent appointment.
The letter states that the TUG executive has passed a motion regarding the new post of 'Editorial Advisor to the Director of Content'.
"The post was created and filled without consultation or advertisement," the letter states.
"There are many union members who would have welcomed the opportunity to apply for the role."
The letter says that as a public service broadcaster RTÉ has an obligation to uphold best practice and to act with transparency in the matter of appointments.
"In calling others to account, RTÉ staff must never be undermined by organisational failures to meet the highest standards of probity," the letter states.
The Trade Union Group says that under a transformation agreement, RTÉ committed to the principle of open competition.
The TUG is calling on RTÉ management to clarify the rationale for the creation of the post and to provide further details about the specific role, function and terms and conditions of employment.
Unions say they are seeking clarification as to why management breached policy in this instance and are seeking assurances from the Director General that RTÉ is committed to the principle of fair and open competition in public appointments at all levels.
"This appointment is all the more regrettable in light of assurances previously that such practices would cease," the letter concludes.
In a statement, RTÉ said it does not comment on any individual employee.
"However, re-assignments do take place across RTÉ," the statement read.