The Government has said it will appeal to the European Court of Justice if no resolution is found to protect the Irish Box, the State's 50-mile fishery exclusion zone.
"We will go all the way on this. Our legal advice is firm," a spokesman for the Minister for Communications, Marine and Natural Resources, Mr Ahern, said yesterday.
The warning follows stalemate at last week's EU fisheries council - and increasing anger among Irish fisherman on the outcome of a deal on quota cutbacks.
The Minister made it clear that a "gentlemen's agreement" between Ireland and Spain, urged by the European Commission in relation to the Irish Box, may not be enforceable.
The Irish Times understands from industry sources that a fleet of up to 200 Spanish vessels which has been tied up since closure of Moroccan fishing grounds is intending to access the restricted zone, established to protect biologically sensitive grounds when Spain and Portugal joined the EU in 1986.
The Minister has expressed concern about possible "difficulties" at sea, amid warnings from the Irish industry that an "armada" of Spanish boats would exercise its right to equal access to the zone from January 1st.
Ireland received support from Portugal on its right to retain the box at last week's council meeting, but was otherwise isolated on the issue, according to Irish fishing industry sources. Industry representatives are to plan a course of action over the box issue, and over the new restriction on days at sea which will affect the north-west whitefish fleet.
The industry is also angry with the Minister over his interpretation of the council's outcome overall, and has accused him of "distorting figures" on quotas.
The limit of nine days' fishing per month was extended to the north-west fleet from Galway to Donegal because of its proximity to grounds west of Scotland and in the North Sea, where severe restrictions on cod are being imposed.
The Minister has defended the deal secured as the "best possible against the odds", but industry representatives have criticised the "positive spin" he has put on the package.
"The Irish delegation worked its butt off, but why couldn't the Minister be more honest about the outcome?" asked Mr Lorcan Ó Cinnéide of the Irish Fish Producers' Organisation (IFPO).
Figures the Minister presented yesterday were criticised by Mr Sean O'Donoghue, chief executive of the Killybegs Fishermen's Organisation.
The Minister disputed the figure of 4 per cent for the Irish quota - despite having 11 per cent of EU waters - maintaining instead that the overall figure was 19 per cent. However, his own advisory group on the Common Fisheries Policy which drew up Ireland's negotiating position at EU level says the overall quota is 4.4 per cent.
"We achieved nothing on allocation of resources at this crucial council, and the Irish Box issue is a mess. The days-at-sea proposal has no conservation logic and is without rhyme or reason," Mr O'Donoghue said.