Former taoiseach John Bruton has warned that Brexit poses the biggest threat to the State's food industry since the economic war in the 1930s.
Mr Bruton said it was likely there would have to be a "goods border" between the Republic and Northern Ireland, particularly for food products on which the EU had a tariff.
If there was free trade between Britain and Brazil in beef, he said, there would have to be checks on the Border to "ensure people were not eating burgers from Brazil".
Mr Bruton was speaking at the Irish Hotels Federation annual conference at the Lyrath Hotel in Kilkenny.
The former EU ambassador to Washington also said there would be “unanimity” among member states in granting the UK an extra year to conclude the “massive detail” of the Brexit negotiations.
Mr Bruton said he did not believe that in two years time Britain would be outside the EU, but he warned the Conservatives would be reluctant to seek or even agree to an extension of another year.
He said British prime minister Theresa May wanted to have the process finalised before the next general election in the UK.
Niall Gibbons of Tourism Ireland told the conference tighter checks could also cause delays on the Irish Sea.
Mr Gibbons said a forecast investment of €150 million in a new ship by Irish Ferries would see capacity for 600 lorries and cars. But he said if there was a delay of just one minute per vehicle it could result in queues of up to 10 hours.
Joe Dolan, president of the Irish Hotels Federation, said that the market for tourists from the North and Britain who were the main clients of tourist facilities along the northwest coast, had to be protected. If they were faced with a two-hour delay on a Friday night "they wouldn't bother", he said.
Dr Howard Hastings of the North's biggest hotel chain Hastings Hotels, which also part owns Dublin's Merrion Hotel, said politicians North and South, had to work with those in Britain to figure out the uncertainties of what will happen post-Brexit.