Ibec has welcomed the 'reality check' early on in the negotiations on free movement across the border post-Brexit.
The group says there has yet to be a serious discussion as to what the implications are for an EU customs border on the island of Ireland.
Yesterday the British Prime Minister insisted free movement of EU workers will end when Brexit takes effect in March 2019.
Earlier this week, the Taoiseach stated that the Irish Government is "not going design a border for the Brexiteers", provoking outrage in the DUP party.
"The onus now is on the UK to ensure a seamless and frictionless border, to come forward with propositions about how that can be managed," Brexit campaign lead for Ibec, Arnold Dillon.
"Because the UK, outside of the EU Customs Union will inevitably demand customs checks, and it's very difficult to see how that will be easily managed along the strip of border between the Republic and Northern Ireland."