A Leitrim TD claims a trade deal between the EU and four South American countries would be a huge threat to Irish agriculture.
The Mercosur agreement would see a boost in free trade between the bloc and Argentina, Brazil, Paraguay and Uruguay.
The European Council is due to decide whether to back it next month.
In the Dáil tomorrow, Sinn Féin will call on the government to strongly oppose it.
Martin Kenny is the party's agriculture spokesman; here’s what he had to say.