SIPTU Deputy General Secretary Gerry McCormack has said there were "problems" from the very beginning of the Covid-19 crisis at meat processing plants.
Speaking on RTÉ's Morning Ireland, he said what appears to have happened is that some employers "ignored completely" the recommendations from the Health Service Executive on physical distancing, and did not put proper measures in place to protect workers.
He said meat processing plants were given guidelines from the HSE, but some did not put protocols in place and is "questionable" whether some should have opened at all.
SIPTU is calling for urgent action to be taken to deal with the clusters of Covid-19 infections in meat plants.
Mr McCormack said the meat industry is essential, not just to provide food here, but to other countries also.
He compared the current situation in the meat industry to the dairy industry, where he said there are very little if any outbreaks of Covid-19.
"It is well paid and well regulated compared to the meat industry," he said.
He also acknowledged that the high number of migrant workers who work in meat factories here, who may be living in close quarters with other workers, could have resulted in some clusters of Covid-19 infections.
Minister for Agriculture Michael Creed is to appear before the Dáil next week to face questions about the increase in cases.
Several TDs raised the issue yesterday after RTÉ News revealed another 60 cases had been confirmed at a meat plant in Edenderry, Co Offaly.
More than 600 workers at meat processing plants have now contracted the virus, according to authorities.
The meat industry said it has been proactive and has made substantial efforts to try to halt the spread of the coronavirus.
Independent TD Denis Naughten has said many people working in the meat processing sector are afraid to speak out about concerns over Covid-19 safety and hygiene measures in meat production plants.
Mr Naughten, a TD for Roscommon and Galway, said that many workers from non-national communities had expressed concerns directly, and he brought it to the attention of authorities.
Speaking on RTÉ's Today with Sarah McInerney, he said there is a lack of communication about when the virus was identified in some meat plants and when action taken.
He said he had been informed that in some facilities there was a six-week delay between the reporting of a confirmed case and the screening of the workforce in that plant.
These workers then continued to work the next day for another week before they got test results.
He said the management of testing and delays in contract tracing in some cases where there has been outbreaks of the virus need to be fully investigated.
He also said there is clarification needed from the Department of Agriculture about what feedback has come back from inspections of infection sites about what measures are being taken to minimise infection.
Mr Naughten said there are huge discrepancies between some production plants where there is over 50% of staff infected and in others where there are very few cases.
Speaking on the same programme, Director of Migrant Rights Centre Ireland Edel McGinley said she is very concerned and worried about the outbreaks in plants.
She suggested measures were not put in place quickly enough to protect against the virus, and said workers do not feel safe. She said they have been contacted by many meat plant workers who are "frightened and angry", and unsure of how they are being protected.
"It is not obvious what is happening at these places of work and whether the situation is being dealt with in any coordinated way," she said.
She said pay is also an issue as there are no proper sick pay schemes, so it is difficult for the workers when they fall sick and apply for social welfare. She said it also raises the question of whether some people are coming back to work too soon.
Ms McGinley said she supports the suggestion that where there are outbreaks of Covid-19 in meat processing plants to close them and reopen when it is safe to do so.
She said it is very difficult for workers with a lack of information and what their entitlements might be. "The onus is on employers to assist people in these situations to apply for sick pay at a lower rate," she said.