New analysis suggests Northern Irish dairy farmers could lose 10 pence per litre in the event of a no-deal Brexit.
Such an event would trigger a 'doomsday scenario' for the industry, the Dairy Council for NI warns.
It is 'questionable' whether farmers could survive no-deal as the group warns many would face a huge decline in milk price.
Northern Irish dairy farmers, who are already witnessing poor prices, could see a 10p per litre slash, the dairy body says.
It adds that more than 3,000 farm families across the province could be threatened with loss of livelihoods and jobs.
Dr Mike Johnston, CEO of Dairy Council NI, said that current trade tariffs for exporting both raw milk and finished product would be in excess of £300m, which would directly result in an impact on the price paid to farmers for their milk.
He said: “Based on calculations in a no-deal Brexit, trade tariffs on both raw milk and finished products moved from NI to the EU would total £320m, before you calculate the cost of the administrative burden customs will place on dairy processors.
“This tariff represents 25% of the value of our entire industry. In a sector where the margin is, at best, 3% or 4%, trade tariffs of that magnitude would wipe out the industry.
“The reality is stark for farmers. Our analysis suggests that the milk price paid to farmers would fall by over 10 pence per litre from its current base should such tariffs be imposed.”
Responding to the Dairy Council's claims, the Ulster Farmers' Union (UFU) said the proposed 'no-deal' temporary tariff regime would be 'disastrous' for NI farmers.
Deputy president Victor Chestnutt said: “Any agreement that restricts trade north-south and east-west will have a severe impact on Northern Ireland dairy businesses.
“We have consistently said that any deal must allow free and frictionless trade and that a no-deal Brexit would be disastrous for Northern Ireland’s family-run farms.”
“Our farmers who are the primary producers, will pay the price for high tariffs ultimately wiping out their livelihoods.
“Any tariffs the EU applies should be reciprocated. The UK should apply tariffs, which includes goods coming into Northern Ireland from the Republic of Ireland,” he said.
The Dairy Council for NI represents milk processors including Dale Farm, Glanbia Cheese, Glanbia Ireland and Lakeland Dairies.
These four companies account for over 90 percent of the 2.4bn litres of milk collected from NI farms each year.
