It has been suggested that if there is a no deal Brexit, customs arrangements on the Irish border should continue as normal, with governments "picking up the pieces" later.
British officials are drawing up contingency plans to prevent lorries being stopped at borders between the UK and the EU.
However, there is still confusion over how that could be done at the border with Northern Ireland.
Some officials have suggested it may be left alone in the event of a no deal Brexit and dealt with later, which Sinn Féin TD Louise O'Reilly says is not acceptable.
"I think when you say 'fix it later' you're really kicking the can down the road and ignoring the problems that are here right now," she said.
"The Taoiseach and the negotiating team have a duty, they have an obligation not just to the people in the 26 counties but to the people on the whole of the island.