Workers at the Vita Cortex plant in Cork have pledged to escalate their protest.
The 32 former staff members have been staging a sit in at the foam manufacturing factory in Ballyphehane since it closed last December- in a dispute over their redundancy payments.
The State has covered two weeks of the workers' statutory payment, but management have yet to pay what the workers claim was the agreed balance of 0.9 weeks per year of service.
Hopes for a resolution to the long-running dispute were dashed this week after management said it could not accept a solution proposed by mediators, which had been accepted by the workers.
"Both sides agreed to enter a mediation process which had two stages to it," said SIPTU official Anne Eager, representing the workers.
"The first stage of the process didn't produce a solution so therefore we moved to the second stage, which was that the mediators - three independent people - issued proposals for consideration by both sides as being their assessment of what was fair and equitable, and would provide the basis for a solution.
"We accepted it and on Friday evening Mr Ronan (Vita Cortex owner Jack Ronan) decided to reject it."
The workers, today on the 136th day of their sit-in, will meet tomorrow to plan their next move.