The dispute at An Post looks set to escalate over the coming days following the Labour Relations Commission’s failure to resolve the differences between the sides.
The LRC held around six hours of talks with An Post and the Communications Workers' Union yesterday, but admitted afterwards that it had failed to make any progress.
An Post has already suspended more than 500 workers at its Dublin mail centre because of their refusal to comply with new sorting arrangements that they say were introduced without consultation.
The matter is part of a larger disagreement between the sides over pay and productivity deals negotiated in the past.