Divisions over fisheries in the Brexit negotiations have deepened, RTÉ News understands.
UK sources have confirmed that London is proposing to remove a large component of fish stocks from the terms of any bilateral EU-UK free trade agreement.
Instead, it will have them dealt with through an annual negotiation with other independent coastal states such as Russia, Greenland, the Faroes, Iceland and Norway.
At the same time, the UK has said it has no intention to renationalise its fishing fleet.
It comes amid suggestions from a number of EU officials that it wants to bar foreign majority investment in the UK fleet for the purposes of calculating fish quotas.
The divisions follow a sharp denial by the EU's chief negotiator Michel Barnier that there had been a breakthrough on the fishing issue last night.
Negotiators are currently locked in talks over the amount of access EU boats will have to UK waters after Brexit, and how much fish quota they will be able to catch.
Quota is generally divided into demersal, or seabed, species such as white fish and prawn, and pelagic species like mackerel, whiting and Atlanto-scandian herring (ASH), which swim near the surface.
It has emerged that the UK wants to strip the pelagic element, said to be worth some 80% of the value of fish caught by European fleets in UK waters, out of the treaty.
It wants to have it dealt with through an informal fish management forum under the auspices of the North East Atlantic Fisheries Commission (NEAFc).
In the meantime, demersal stocks would be handled through the bilateral EU-UK free trade agreement.
EU officials have expressed alarm at the suggestion.
They argue that the NEAFc forum is informal and not legally binding, and that it will lead to the overfishing of stocks such as mackerel, since its members historically breach quota limits.
From 1 January, the UK will join NEAFc as an independent coastal state.
The UK will then technically control the largest share of mackerel in EU waters, unless an agreement is reached beforehand with the EU on mackerel stocks and access to mackerel fishing grounds.
Both EU and UK officials acknowledge that the UK would have dramatically more leverage as a member of NEAFc, and could essentially decide how much mackerel quota it will catch in a given year.
The EU has been in dispute with Iceland and the Faroe Islands in recent years over quota breaches.
Officials say the informal nature of the forum means that stocks are regularly overfished.
"We sign an agreed record, but it's a gentlemen's agreement," says one EU official familiar with the issue.
"This is how much we're going to fish; this is how much you're going to fish, and we all promise faithfully this is what we're going to do.
"There is no encouragement to reach an agreement.
"We've been messing around with Iceland for a full decade now and there's no sign of us ever reaching an agreement with them.
"So, if [Iceland] can ignore the very strongly held views of a large trading partner, the EU, imagine what the UK will do."
A UK source has confirmed that London has tabled a proposal to have the pelagic stocks dealt with under the NEAFc.
However, the source insisted it was designed as a way to simplify the fisheries issue, which has plagued the negotiations for months.
It is understood that Michel Barnier, the EU's chief negotiator, raised the issue during his briefing of EU ambassadors this morning.
An official from one coastal member state described it as "very concerning".
UK officials have also confirmed that they are proposing to attach conditions to the ownership of UK vessels by foreign owners.
However, sources have denied that this would amount to the re-nationalisation of the UK fleet.
In 1990, the European Court of Justice struck down a UK law that required majority British ownership of any vessels that were registered in the UK.
The case, known as the Factortame case, was taken by a group of Spanish trawler owners who complained the requirement was contrary to EU law.
A British source said the UK would simply seek to codify in UK legislation requirements currently available under EU law, which would require owners to be more closely tied to the economy of the UK if they decide to register a vessel there.
The source said the issue had already been agreed by both sides, and had been part of a consultation in the UK, which followed a white paper on the future of British fishing.