The Department of Foreign Affairs has said efforts are continuing to resolve the dispute between Ireland and Britain over ownership of Lough Foyle.
It follows a claim by Northern Ireland Secretary James Brokenshire that the whole of the lough is owned by the UK.
Since partition in 1922 ownership of Lough Foyle, which lies between Donegal in the Republic and Derry in Northern Ireland, has been claimed by both Ireland and the UK.
Currently the area is regulated by a cross-border body set up under the Good Friday Agreement.
Now though Britain's claims have been reinforced with Mr Brokenshire saying all the lough belongs to the UK.
Sinn Féin said that was arrogant and provocative and called on the Government to challenge it.
In response, Minister for Foreign Affairs Charlie Flanagan said Ireland has never accepted the UK's claim to the whole of Lough Foyle.
He said talks are ongoing between both governments in an attempt to resolve the complex issues relating to both Lough Foyle and Carlingford Lough.
The Department of Foreign Affairs issued a statement today saying Ireland has never accepted the UK's claim to the whole of Lough Foyle.
"Uncertainty concerning the extent to which each side exercises jurisdiction within Lough Foyle has created practical difficulties for the conduct of a number of activities there.
"This has included difficulty in creating a system for licencing of aquaculture by the Lough's agency in accordance with the intentions of the two governments under the 1999 agreement establishing North/South implementation bodies."
The statement says that following discussions in 2011 between the then Minister for Foreign Affairs and the British Foreign Secretary, both governments agreed to seek to address and resolve jurisdictional issues relating to both Lough Foyle and Carlingford Lough.
The Department says that since that time a series of meetings have taken place at official level between the Foreign and Commonwealth Office and the Department of Foreign Affairs and Trade.
"The issues involved are complex and involve a range of different actors, including the Crown Estates.
"This is not something we currently envisage as forming part of the negotiations around the UK's departure from the EU", the statement says.