The Irish Farmers Association has said that all beef imports into the European Union should be "suspended immediately" in the event of a no-deal Brexit.
The IFA President, Tim Cullinan, said that the Mercosur Trade Agreement - which would allow for the import of large volumes of beef into the EU - should also be suspended in the event of a no-deal.
He said that the export of beef to the United Kingdom could be severely impacted by tariffs if there is a no-deal.
Mr Cullinan told the Oireachtas Agriculture Committee that he would be very concerned that the UK could do a deal in beef imports with a third country in the event of a no-deal.
Ireland is just weeks away from a possible "Doomsday scenario" says @voteTimLombard a no deal Brexit could have the biggest impact on the agri sector since the 1950's he tells Committee & he questions the readiness of the agri-food sector— Fran McNulty (@franmcnulty) December 8, 2020
He said such a development could see the importation of cheap beef or chlorinated chicken.
Irish beef would need an EU export outlet in that event, he said, adding that he had support from many people in Brussels in addressing that situation in the event of a no-deal
Mr Cullinan said Ireland's dependence on the UK as an export location for food was worth €5.5bn last year, and the IFA estimated that the imposition of tariffs on that level of exports could cost €1.5bn per year.
If that situation transpires, he said, the sector will need what he described as "proper compensation".
Meanwhile, Mr Cullinan also hit out at Bord Bia, accusing the organisation of failing to find new markets ahead of Brexit.
He told the committee that it was now too late, but he has been asking them to do this for the past two years.
Bord Bia, a semi-state body, responsible for marketing Irish food, drink and horticulture, has previously calculated that 37% of Irish food exports go to the UK.
Mr Cullinan said that there was particular need for alternative markets for Irish beef. He told the committee that "there's no point looking for them this evening when we're at the crisis point".
The IFA President was responding to a question from Senator Paul Daly who asked if new opportunities might arise from Brexit.
He noted that UK potatoes, used to make chips, could be prevented from entering Ireland after Brexit.
Tim Cullinan said that growing this type of potato, known as table or seed potato, would take considerable time. However, he said that the IFA will be looking into this possibility with members.
Separately, Mr Cullinan said there are many vegetable growers in Ireland who lose out during Christmas each year, when supermarkets lower their prices. He said it was not unusual to see vegetables imported from abroad while Irish vegetables were left in the ground.
He said it was important that retailers choose Irish produce and he hoped consumers would support Irish goods as well.
Vice President of the Irish Natura and Hill Farmers Association, which represents farmers on marginalised, hill and designated land, said that Brexit could provide an opportunity for Ireland to be more self-reliant.
Henry O'Donnell said that sheep farmers would be able to step-up production "in a relatively short time-span" if they thought it was worth their while.
Additional reporting: Tommy Meskill