Long-term planning and preparation is required for a united Ireland, an Irish senator has said.
Mark Daly said the Brexit crisis showed the unforeseen consequences of holding a referendum without proper preliminary steps.
Taoiseach Leo Varadkar has previously warned that now is not the time to prepare for a referendum on a united Ireland.
Mr Daly said: "The major lesson for Ireland from the Brexit crisis is the unforeseen consequences of holding a referendum without proper planning.
"A united Ireland requires long-term planning and preparation with all sides."
He analysed court documents from victims' campaigner Raymond McCord's recent legal challenge surrounding Brexit.
Mr Daly said: "As it stands, a referendum on a united Ireland could potentially be decided by the Secretary of State before a single vote is cast.
"The Secretary of State for Northern Ireland cannot say the majority are or are not in favour of a united Ireland until it is decided who will be allowed to vote in a referendum."
He said there was an urgent need for more policy and greater clarity.
Mr Varadkar has said the time is not right to begin official planning for a referendum on Irish unity.
A recent poll revealed more than two-thirds of voters in Northern Ireland believe Brexit will make a United Ireland more likely within the next 10 years.
Senator Daly said: "My response to the Taoiseach is that policy neglect seldom goes unpunished and we are well aware that Northern Ireland has a tragic history of denying people the right to vote. The future referendum on a united Ireland cannot be another chapter in that story."
Meanwhile, yesterday a report said Ireland should have a central role in shaping the EU peace project.
The bloc should provide a pluralist "European roof" for the process of Irish unification, its authors said.
It said: "If the EU takes seriously its own foundational values, and its commitment to the Good Friday Agreement in all its parts, then planning and preparation for the moment when the principle of consent will be tested must begin now; it should form one part of the ongoing negotiations between the EU and UK. There is an opportunity for the EU to ensure that the island of Ireland continues to have a central role in shaping this supranational European peace project.
"Northern Ireland has an agreed way back and, in our view, the institutions of the EU can and should function in a supportive role by clarifying the consequences of this choice and facilitating a managed transition to new arrangements."
The document entitled: The EU and Irish Unity: Planning and Preparing for Constitutional change in Ireland, was authored by Professor Colin Harvey, from QUB, and barrister Mark Bassett.
Sinn Fein MEP Martina Anderson attended the report launch. She said: "It's right that we prepare and plan for constitutional change on this island. The EU have a role in that, too."