The Republic's secretary general at the Department of Agriculture has said his department is preparing for the "worst outcome" of the upcoming Brexit negotiations, including the return of a hard border with Northern Ireland.
Speaking at a hearing of the public accounts committee in recent days, Aidan O'Driscoll said the Republic's Department of Agriculture is concerned about the practicalities of managing any kind of border with exports and imports after Brexit.
"I have told several sectoral groups that we have to negotiate strongly and clearly for the absolutely best outcome.
"We also have to prepare for the worst outcome. It would be foolish not to do both of those things," he said.
Mr O'Driscoll described Brexit as the most important negotiation the agri-food sector has faced since the 1972 negotiations to enter the-then EEC.
"The UK accounts for approximately 40% of (Republic of Ireland) agri-food exports," he said.
"Some sectors are much more exposed than that.
"About 50% of our beef exports, for example, go to the UK.
"This is particularly crucial because the UK beef market is the highest priced beef market in the world. Accordingly, the importance of that to the beef sector is obvious."
Within the dairy sector, the exposure is somewhat less, he said.
However, he highlighted that within some sub-sectors there are a range of problematic issues.
"For example, we produce a lot of cheddar cheese in this country, of which 60% goes to the UK.
"This is a particular challenge because no one eats cheddar in such quantities.
"We cannot just divert the cheddar off to France.
"There are many challenges built into Brexit," he said.
Mr O'Driscoll stressed to the committee that the Department of Agriculture has already began preparations for Brexit.
He said: "The Minister for Agriculture, Food and the Marine has pointed out on several occasions in public that the day he was appointed I handed him a large file of briefings, a large chunk of which were on Brexit.
"It showed the research work we had done well in advance of the UK referendum.
"We have set up an elaborate process of consultation with stakeholders, which is our norm in major negotiations.
"We have done this before in Common Agricultural Policy and trade negotiations."
Mr O'Driscoll added that negotiations were ongoing.
"Our demand is crystal clear. We want to retain unfettered access to the UK market after whatever happens," he said.
"We also want to keep the UK market as a valuable market for the future."