SIPTU says it has anecdotal evidence where people in the meat industry are being told to come to work or they may not have a job.
Members of SIPTU will meet with Meat Industry Ireland later to discuss the hundreds of COVID-19 cases in processing plants.
They have been linked with a large portion of positive tests in Kildare, Laois and Offaly and led to a local lockdown.
It is believed 150 workers have tested positive at the Kildare Chilling facility, another 86 at O'Brien Fine Foods in Timahoe and nine at the Irish Dog Food Factory in Naas.
All the facilities have suspended production.
Carroll Cuisine in Tullamore, which has reported nine cases, remains open but is undergoing a deep-clean.
Greg Ennis, SIPTU divisional organiser, told Newstalk Breakfast: "This would be I suppose somewhat a historic meeting - the first time that Meat Industry Ireland have met with trade unions.
"Basically what I'll be saying to them is that meat may be perishable but workers are not.
"We've had 10% of the workforce in Ireland affected by COVID, and I'll be saying that the unbridled drive for turnover and profit must not be at the cost of workers health and indeed others in the community.
"And while there's nothing wrong with reasonable profits in any industry, and we support that, there also must be reasonable terms and conditions for the workers who generate those profits.
"So what we'll be saying to Meat Industry Ireland is that we will have a protocol to put to them, or our SIPTU charter as I call it.
"We will be looking for them to support our cause for repeat blanket testing of all workers in the Irish meat processing industry on a 14 to 21 day cycle.
"We'll be looking at commonality of purpose from them - where COVID is suspected, or is in fact in place, workers must be removed from those work areas without loss of earnings.
"And we'll be looking for them to agree to commence a talks process with SIPTU... to agree what we believe are reasonable terms and conditions.
"At the moment, we have a situation where nine in 10 workers for example do not even have a sick pay scheme.
"And that is all contributing to the transmission of COVID, because workers are forced into work on the basis that they have nothing else to rely upon".
"We have anecdotal evidence where people are being told to come to work or they may not have a job."
"But when you don't have sick pay and you're earning somewhere just above the minimum wage, it is very very difficult - unless you're really sick - not to go into work because you've nothing to fall back on".