Trawlermen in Scotland have warned that European Commission concessions will not be enough to avoid a crisis in the industry.
Skippers are threatening not to tow the line on fishing curbs.
Fishermen's leaders warn the moves to protect fish numbers will still lead to the haddock industry being sunk.
Skippers complain the deal struck in Brussels before Christmas, aimed at saving fragile cod stocks, is not workable - and will bankrupt the fleet.
Industry chiefs argue that changes to the plans will only delay the closure of Scotland's haddock fishery.
Conservation measures mean fishermen are limited in the amount of haddock they can land and are restricted to 15 days at sea every month.
Scottish Executive officials have been telling industry leaders about the commission's latest thinking.
They met in Edinburgh on Tuesday, when fishermen were told that some changes were being considered.
But the chairman of the Scottish White Fish Producers' Association, Mike Park, argued that the proposed changes to December's "disastrous" deal in Brussels were no more than a step in the right direction.
The Scottish Fishermen's Federation's Hamish Morrison insisted that the industry was now running out of patience.
Skippers may now pursue a legal challenge to the restriction on the days they are allowed to put to sea.
The executive said it could not speculate on the outcome of its negotiations with the commission.
However, a spokesperson said there may be some relaxation of the days at sea restrictions to ensure boats are not penalised if, for instance, they lose fishing time while going to help a vessel in trouble.