Fianna Fáil leader Micheál Martin has said the party is putting together a white paper on what a reunified Ireland would mean in a practical sense if a referendum on the matter was to be held and passed.
Mr Martin said he believed arrangements would include the continuation of parliaments both North and South.
Other matters such as integrating education and healthcare systems would have to be considered.
Speaking on RTÉ's Today with John Murray, he added there should be all-island agencies such as Enterprise Ireland and the Food Safety Authority.
Mr Martin said that anyone who is interested in a united Ireland should have a blue print on the matter, and that there was an obligation to spell out how a united Ireland would work.
Pointing to the uncertainty and confusion caused after the UK voted to leave the EU, Mr Martin said there was a need to be aware of politicians promoting the idea of a referendum without having "the foggiest idea what will happen the day after it passes."
Sinn Féin demand unity referendum as Brexit trigger looms
Sinn Féin has said there is an urgent need for a referendum on Irish unity as the British government has "refused to listen" to the majority of people in Northern Ireland over Brexit.
Michelle O'Neill, Sinn Fein's leader in the region, said the British government was "on the verge of triggering Article 50 that is going to take the North out of the EU against the expressed wishes of the majority of people here".
She added: "They are continuing to refuse to listen to the majority views. Brexit would be a disaster for the economy and the people of Ireland.
"To us in Sinn Fein that increases the urgency for the need of a referendum on Irish unity and that needs to happen as soon as possible."
Calling for unity referendum is not a new call for Sinn Féin.
Minister for Foreign Affairs Charlie Flanagan said calls for an Irish border poll were "premature" and an issue for the longer term.