No-deal Brexit contingency plans to allow Irish imports from mainland Europe to bypass UK inspection regimes may not work, Greencore boss Patrick Coveney has warned.
Mr Coveney, the brother of Tánaiste Simon Coveney, told the Irish Independent that the chaotic fallout could see truck drivers in long queues at the ports of Calais and Dover blocking goods which are destined for Ireland.
"If you end up with some logjams in Dover and Calais, which you might, are British truckers going to stand aside and let stuff pass through just because they've [the UK and Ireland agreed]?" Mr Coveney said.
"We don't know and won't know until we get to [a no-deal Brexit]."
This could create risks of shortages with food products that Ireland cannot grow during the autumn and winter such as strawberries, lettuce, peppers and tomatoes, he added.
One of the country's largest retailers, Tesco, has already warned that a no-deal Brexit at the end of October would be more difficult than it would have been at the end of March.
The company will have less storage capacity later in the year as it stockpiles goods in the run-up to Christmas.
The Central Bank has also warned of potential food shortages in the event of no-deal.
Ireland is heavily reliant on the so-called UK landbridge, which provides for the movement of Irish exports and imports to and from the EU using the UK road and port infrastructure.
Three million tons of Irish traffic goes via the landbridge annually including many time-sensitive food imports.
In a no-deal scenario, Ireland will rely on the customs transit procedure to avoid any duties or taxes when goods are moved through the UK. The Government said in its most recent no-deal Brexit contingency document that "considerable progress has been made in application of EU rules and an agreed understanding has been reached on continued use of the landbridge under the internal transit procedure".
But Mr Coveney has questioned whether this will be sufficient to avoid delays in goods, including many food imports, reaching Ireland from continental Europe.
"There has been a fair level of preparation around products that are intended for Ireland in a no-deal scenario that it will be sealed differently on trucks and containers from continental Europe before it goes through Dover," he said.
"The idea is technically that they can bypass the inspection regimes that will have to happen for products coming into the UK,
"The theory is fine but if the ports get clogged up, which I think they will, the idea that behaviourally truck drivers will stand by and allow them to pass through Dover is questionable."
Mr Coveney's warning comes in the wake of the leaking of UK government warnings that cross-border agri-trade in Northern Ireland "virtually stops" on the first day of a no-deal Brexit.
So this is no-deal Brexit and what have you done, dear Taoiseach? What have you done, beyond the backstop (which is fragile), to get the EU to help cushion us against a Brexit-triggered downturn? And what has your Government done to prepare our economy, and ensure workers and families are protected?