Ibec has called for an extended Brexit transition period - even in the case of the UK leaving the EU with no deal agreed.
Reacting to fresh no-deal Brexit contingency plan requirements from the European Commission, the employers' body said more meaningful measures are needed to support businesses, including a comprehensive range of state aid supports in order to protect companies and jobs.
"Reckless time-wasting by the UK government is now forcing businesses to activate costly no-deal contingency plans. A comprehensive Brexit deal has been agreed and signed off by the UK Cabinet. If the UK government is unable to ratify it, it should defer or cancel Brexit," said Ibec's director of policy and public affairs Fergal O'Brien.
"Adjusting to a radically new trading relationship with the UK at the end of March is not possible and not realistic. Acute trade bottlenecks would be created overnight. Jobs and businesses would be immediately on the line. Companies are preparing insofar as they can, but the economy is simply not in a position to deal with such an unprecedented and profound shock. An extended transition period would be required, including in the case of no-deal," he said.
Last month Ibec forecast 4.5% growth for the Irish economy next year, solely based on the UK sealing a positive Brexit deal.
Elsewhere, industry representative group the Killybegs Fisherman's Organisation has said a no-deal Brexit would be an "unmitigated disaster" for Irish fisheries.
"Ireland’s two biggest fisheries, mackerel and prawns, are massively dependent on access to UK waters with the overall percentage of stocks currently fished from UK waters by the Irish fleet standing at more than 30%. We cannot countenance a situation whereby this access might stop at 11pm on March 29 next due to a hard Brexit," said KFO chief executive Seán O'Donoghue.
Meanwhile, a survey by PwC of Irish-based finance chiefs has shown that while 57% are upbeat about the near-term prospects for the Irish economy, only a third are "very prepared" for Brexit, in any form.