The Irish Farmers Association says the EU's newest trade deal will be another nail in the coffin for the beef sector here.
The Mercosur deal would allow for greater imports from Latin American countries to the EU, including cheaper beef.
President of the IFA Joe Healy says the increase in beef imports will be highly damaging for Irish farmers.
"It'll be hugely negative, and particularly for the beef sector - a sector that is already under pressure price wise, Brexit wise, food trend wise," said Mr Healy.
"And this is another nail in the coffin and it is something that we need to ensure that beef farmers are safeguarded against as we go forward."
Last night, the Taoiseach said Ireland will vote against the controversial trade deal if it proves to be bad news for Irish jobs and farmers.
Leo Varadkar said there will need to be an economic assessment before a decision is made.
"This would go to the trade council for a qualified majority vote in about two years time so there is a long way to go yet," said Mr Varadkar.
"What we will do now is an economic assessment of the Mercosur deal to see what impact it will have on the Irish economy and on jobs.
"If it is going to have a negative impact on the economy and jobs then obviously we will vote against it."
