A storm has blown up between Scotland and the Republic of Ireland over access to fisheries near Rockall, a tiny islet in the north Atlantic.
The Scottish government in Edinburgh has warned Dublin it will enforce its fishing rights in the area, where Irish trawlers have caught squid, haddock and other species for decades.
Scotland's external affairs minister Fiona Hyslop said her government would deploy fisheries protection vessels to enforce a 12-mile exclusion zone around the islet, which lies some 260 miles off Scotland's west coast.
In a letter, she told the Dublin authorities: "Irish vessels or any non-UK vessels for that matter have never been allowed to fish in this way in the UK's territorial sea around Rockall and, despite undertaking extensive discussions with the Irish authorities on the matter, it is disappointing this activity continues.
"There has actually been an increase in that illegal activity and, with the Rockall fishery season nearly upon us, it is our duty and obligation to defend the interests of Scottish fishermen and ensure compliance with international law."
Dublin disputes the Scottish claim to the rich fishing grounds around the uninhabitable islet.
Irish Foreign Minister Simon Coveney rejected the Scottish claim: "It has been and remains that the waters around Rockall form part of Union waters under the Common Fisheries Policy, to which the principle of equal access for the vessels of all EU member states applies.
"We have never recognised UK sovereignty over Rockall and accordingly we have not recognised a territorial sea around it, either.
"We have tried to work positively with the Scottish authorities and to deal with sensitive issues that flow from it in a spirit of kinship and collaboration
"We very much regret that matters have reached this point and intend to do everything possible to achieve a satisfactory resolution," the Irish Foreign Minister said.