Fianna Fáil leader Micheál Martin has called on Jobs Minister Richard Bruton to meet with workers at Vita Cortex in Cork as a matter of urgency.
Mr Martin has described the treatment of staff as "appalling" and said everything must be done to ensure the company pays its staff the redundancy they are owed.
"What is happening here is nothing short of disgraceful," Mr Martin said.
"The Vita Cortex employees were promised as far back as September that they would be paid redundancy of 2.9 weeks per year of service.
"Now, after years of working at the plant and providing good honest service, they have been betrayed.
"It is a disgrace that they have to occupy the building to have their voices heard. I fully support their action, and I am calling on the Government to intervene and do the right thing before this escalates further."
Yesterday, SIPTU also called on Minister Bruton, as well as business body IBEC, to intervene in the dispute.
The union, which represents the workers, also said it is prepared to launch a nationwide campaign if staff at the foam packaging plant in Cork are not properly paid.
Thirty-two Vita Cortex workers were let go without proper redundancy pay last month, after NAMA froze the company's assets.
They have been staging a sit-in at the premises ever since.