Brexit has sparked its first territorial dispute – reigniting an ancient row over the ownership of Lough Foyle.
Claims over the vast estuary between Co Londonderry in Northern Ireland and Co Donegal in the Republic have been made since the island was partitioned almost a century ago.
After the Good Friday Agreement peace deal, a cross-border body called the Loughs Agency was handed responsibility for the waters, a key strategic naval base during the Second World War.
But in the wake of the UK’s vote to leave the European Union, Northern Ireland Secretary of State James Brokenshire has reasserted London’s claim over the entire lough.
In response, Dublin issued a fresh declaration saying it does not see Lough Foyle’s disputed ownership being put on the table as part of the Brexit negotiations.
Mr Brokenshire was asked in a parliamentary question how fishing rights will be decided in both Lough Foyle and Carlingford Lough – which also straddles both jurisdictions – after the UK leaves the EU.
The Conservative minister said London is committed to withdrawing from the EU Common Fisheries Policy and putting a new fisheries regime in place.
But no actual decisions have yet been taken, he said, adding that the UK was bound by international law.
He said: “The Government’s position remains that the whole of Lough Foyle is within the UK.”
Dublin’s Department of Foreign Affairs swiftly rejected the claim.
“Ireland has never accepted the UK’s claim to the whole of Lough Foyle,” it said.
Sinn Fein Senator Padraig Mac Lochlainn branded Mr Brokenshire’s remarks as “arrogant” and provocative”.
“The Loughs Agency tasked with responsibility for managing Lough Foyle by both governments has been repeatedly calling for a resolution so that the real tourism and fisheries potential of the Lough can be fully realised,” he added.