Scottish fishermen have condemned a decision by Iceland to increase its mackerel quota unilaterally by nearly 17,000 tonnes next year.
The move is the latest twist in the so-called "mackerel wars" that have placed Iceland and the Faroe Islands at odds with the European Union and Norway.
Iceland has set a 2011 quota of 146,818 tonnes, up from 130,000 this year.
The Scottish Pelagic Fishermen's Association said the move could result in serious harm to the health of stock.
Talks aimed at resolving the row over mackerel quotas broke down earlier this month, with the Faroe Islands and Iceland at odds with the EU and Norway over catch levels for 2011.
The EU and Norway plan to catch up to 583,882 tonnes out of a recommended total allowable catch of nearly 650,000 tonnes.
Icelandic officials said the EU and Norway had "disregarded the legitimate interests" of the other coastal states.
Icelandic negotiator Tomas Heidar told the BBC Scotland news website his country's quota for 2011 ensured an unchanged share of 16%-17% for Iceland in mackerel fisheries next year.
He said the decision by the EU and Norway to take more than 90% of the total allowable catch recommended by scientists was "totally unjustified" and amounted to a decision to overfish mackerel next year.
He added: "The EU and Norway are not the sole owners of the mackerel stock and by taking almost all the recommended total allowable catch, they disregard the legitimate interests of the other two coastal states, Iceland and the Faroe Islands, as well as the interests of Russia."
But both the Scottish Pelagic Fishermen's Association (SPFA) and Scottish Fisheries Secretary Richard Lochhead said they condemned Iceland's move.
SPFA chief executive Ian Gatt said the decision smacked of desperation and was "sheer political posturing".
He continued: "Considering that Iceland never even fished for the species prior to 2005, their decision to significantly increase even further an already grossly over-inflated quota is the height of irresponsibility and could do real damage to a stock that has been sustainably harvested and carefully looked after by the Scottish fleet."
Mr Lochhead said the decision by Iceland represented a "flagrant disregard" for fisheries conservation and international opinion.
He continued: "It is now more important than ever that the international community stands together and takes strong action before it is too late for one of Europe's biggest and most valuable stocks.
"We have a commitment from the EU Fisheries Commissioner Maria Damanaki to take strong action against Iceland - and the Faroes - and put in place the necessary tools to apply meaningful sanctions.
"The valuable mackerel fishery - worth £135m to the Scottish economy in 2009 - has been sustainably managed for the past 10 years by Scottish fishermen, as well as others across the EU and Norway."
He added: "Firm action is vital or the irresponsible practices of Iceland may lead to the demise of this fishery."