SIPTU has called for a contingency fund to support workers affected by a no-deal Brexit.
In a statement, Deputy General Secretary Gerry McCormack cited the agri-food, fishers, aviation, road transport, pharma-chemical, electrical machinery, retail and wholesale businesses as being most at risk from Britain crashing out of the EU without a deal.
He noted that the Government has directed additional funding to vulnerable businesses to help them to prepare for Brexit and, if necessary, diversify their operations.
However, he said there had been scant mention of extra support for workers who could be affected.
He said it would not be sufficient to rely on the EU Globalisation Fund, as that only applies to very large firms - so a new contingency fund would have to established to enable workers to adjust post-Brexit.
SIPTU Manufacturing Division Organiser Teresa Hannick highlighted particular concerns among workers in the border region.
She said that while the Government has reiterated its commitment to avoiding a hard border on the island, there is no clarity on how this can be achieved if the UK leaves the European Union under World Trade Organisation rules.
She cautioned that this could cause major disruption to north-south trade and put jobs at risk, while the requirement for animal and food checks could also put great strain on east-west agri-food trading.
SIPTU researcher Loraine Mulligan noted that the EU contingency plans establish a temporary fix for UK flights and is an attempt to guarantee citizens' rights.
However, she said the ball was in the UK Parliament's court - and urged MPs to pull back from the brink by either accepting the withdrawal deal, or by extending or unilaterally halting the Article 50 process.