The Government is under fire over its failure to outline detailed contingency plans for a no-deal Brexit with less than nine weeks to go.
It came after European Affairs Minister Helen McEntee suggested the Government may not reveal arrangements for cross-Border trade until three weeks before the October 31 deadline.
Meanwhile, Business Minister Heather Humphrey warned businesses to prepare for the worst outcome, while still failing to set out the Government's plans.
There are mounting fears of a crash-out Brexit amid the escalating political crisis in the UK after Prime Minister Boris Johnson moved to suspend the British parliament on Wednesday.
Fianna Fáil business spokesman Robert Troy said: "It's as obvious as a nose on our face that the Government needs to urgently step up our preparations for a no-deal Brexit. They can start by telling people exactly what their plan is."
Mr Troy said exporters had been "unable to get a straight answer" when they ask where the Border checks would be if no deal comes to pass.
"With only weeks left to D-Day there remains far too high a level of unpreparedness," he added.
There was further pressure from business lobby group Isme. Its chief executive, Neil McDonnell, said "we really are into the 11th hour" but he can't advise members on what will happen in relation to customs and veterinary checks.
He said if checks were to take place away from the Border - as mooted in talks between the Government and the European Commission - "what does that look like and what do we need to do? If someone rings me up today and asks about it, I can't say".
He added: "The Government is going to have to start saying... quite soon that 'we know we have this in hand and we are going to announce plans'."
It came after ministers were challenged on the lack of details for businesses and Border communities.
The Government has been in talks with the commission about how to avoid extra Border infrastructure while protecting the EU single market and customs union.
The solution on the table includes checks away from the Border - at points of origin and destinations such as factories, farms and ports.
However, with just nine weeks to go until the deadline, little is publicly known about how such arrangements would work.
Ms McEntee said the Government was still working on the issue.