The EU's new deal with the Mercosur bloc of South American countries will "decimate" the beef market here, according to the Irish Farmers' Association.
Speaking on RTÉ's This Week programme, the IFA's National Livestock Chairman Angus Woods said farmers were not overreacting to the deal, and that it will be devastating for Irish beef farmers.
Mr Woods said the consequences of the deal would be worse than a hard Brexit and that the beef coming through from South America would not be the same quality, and was sub-standard.
He said that Irish beef farmers were producing their beef by European standards and argued the deal would impact on every parish around Ireland.
Mr Woods said the EU Commission believes there is a massive win in this for other sectors, and that it is willing to let the beef industry "take a hit" to achieve it.
He added that the IFA will fight the deal and called on the Minister for Agriculture Michael Creed to get together with his EU counterparts and push back against it.
Meanwhile, Minister Creed said the Mercosur trade bloc is a bad deal for the beef sector in Ireland.
Speaking on the same programme, Mr Creed said there was a significant downside to the deal, and that the balance of it was wrong.
"I accept that in the concept of trade agreements generally there is an element of give-and-take and we benefit internationally from trade agreements in terms of opening new markets, but the balance in this one is wrong," he said.
Mr Creed said the current situation has an outgoing commission that is potentially putting things in place that the incoming one might end up changing.
The minister said it is a bad deal for the beef sector and there was no point saying otherwise.
Ireland is not without allies across Europe in pushing back against the deal given its impact on EU farmers, he said, adding that no EU member state has yet ratified or endorsed the deal.
Asked if there was pressure to take any potential hit from the deal given support from other countries against Brexit, he said he did not think that was the case.
Mr Creed said there is always an element of give-and-take when it comes to making deals, but said the deal is not the deal until it is signed off on.
He said what will be seen now will be a lot of interaction among member states and the European Commission to check legal boxes in order to ratify the deal.
Also speaking on the same programme, Fianna Fáil's Charlie McConalogue said the Government has been weak in relation to the deal, and that now farmers worst nightmares are coming true.
He said what farmers need to see now is the Government standing up for farmers' interests at a European level.
He said beef produced in Ireland is done so efficiently, and that the carbon footprint on beef production in South American countries is very, very high in comparison.
He said the Government needs to get its act together and oppose it, and see what rationale the EU Commission was using when it came to agreeing the deal.
Mr McConalogue said the Government has been "asleep at the wheel" on the issue.