The Minister for Communications, Marine and Natural Resources, Mr Ahern, says he intends to "vigorously defend" the integrity of the Irish Box fishing zone, which is under legal threat from Spain.
A legal opinion prepared for the EU Council questions the right to restrict access to fishery areas beyond 12 mile limits - as is the case with the 50-mile Irish Box.
The so-called box was designated as a "sensitive area" when Spain and Portugal joined the European Union in 1985, given that Spain had then (and still has) the largest fishing fleet in the Community.
Mr Ahern is due to meet his counterpart and holder of the Danish presidency, Ms Mariann Fischer Boel, in Copenhagen today, and the EU Agriculture and Fisheries Commissioner, Mr Franz Fischler, in Dublin on Monday. He says retention of the box will be a top priority on his agenda.
"The Irish Box was a political decision, designed to protect Irish waters, and not a legal one," a spokesman for the Minister said yesterday. "We will have our own legal opinion to copperfasten this."
Irish fishing industry representatives have reacted with alarm to the EU Council's legal opinion, which is now in the hands of the Danish presidency at a time when the Common Fisheries Policy review is due to be completed.
"If the Irish Box goes, the consequences will be disastrous," Mr Jason Whooley of the Irish South and West Fishermen's Organisation said.
It would pose a major threat to the viability of ports in the south-west, he said, where fishing contributed approximately €50 million annually. "Scientific advice clearly shows that this box is a hugely important breeding ground and spawning area for a wide variety of fish species," Mr Whooley added.
"Increasing effort on these grounds, which are subject to three of the commission's four stock recovery programmes, is simply illogical."
Yesterday, a spokeswoman for the European Commission told The Irish Times that she could not comment on a document which had been prepared for the council.
The spokeswoman said that the Commission's own "road map" for the future proposed that from January 1st next, access to resources beyond 12 miles would be based on council decisions in conformity with the objectives of the Common Fisheries Policy.
It also says that derogations to the principle of free access, such as the Shetland Box, would have to be reviewed to ensure that only those justified by conservation purposes could be maintained.
It makes no mention of the Irish Box.
Ironically, the level of illegal fishing within the Irish Box could strengthen Ireland's case for the box to be maintained.
Since 1994, when accession arrangements for the box were reviewed, at least 70 per cent of fishing activity in Irish waters has been focused in this area - much of it by Spanish "flag of convenience" vessels.
The threat to the Irish Box is expected to put further strains on an informal alliance of six EU states - Ireland, France, Spain, Portugal, Italy and Greece - which opposes further reductions to the fishing fleet as proposed by the EU commissioner.
The fleet cuts would involve scrapping more than 40 per cent of Ireland's whitefish fleet.
Mr Ahern's meeting in Copenhagen today is part of a "very active" diplomatic mission aimed at selling Ireland's case in the review of the Common Fisheries Policy, in advance of his talks with Mr Fischler on Monday.
Earlier this week, he met the Portuguese fisheries minister, Mr Armando Sevinate Pinto, and pledged to continue the informal alliance.
He said he had also won Portugal's support for retaining the Irish Box.
"We have common interests in ensuring that this very important fishing area is protected from additional fishing activity so that stocks are protected," according to the Marine Minister.
With the December deadline fast approaching, the Danish EU presidency is working towards bringing forward compromise proposals on Common Fisheries Policy reform.
The December council will also be faced with scientific advice on annual quotas which includes a recommendation for a zero cod catch in the North Sea and Irish Sea.