Scotland's fishermen have threatened the SNP government with legal action if it presses ahead with a controversial plan to force them to land more of their catch in Scottish ports.

Fergus Ewing, the Rural Economy Minister, unveiled proposals that would mean Scottish trawlers would be refused a sea fisheries licence unless they agreed to land at least 55 per cent of their fish north of the Border.

But the Scottish Fishermen’s Organisation (SFO) told the Telegraph the move would cost pelagic fishermen thousands of pounds each as they would be prevented from selling their catch to processors in other countries that pay up to 20 per cent more.

John Anderson, the chief executive, warned he had legal advice that the move would contravene competition laws governing the EU single market by preventing them exporting their produce to other member states of the European Economic Area (EEA).

In a pointed attack on the SNP’s desire for an independent Scotland to join the EU, he questioned how this was consistent with wanting to ignore the basis of the single market and warned legal action would follow.

Relations between the SNP government and Scotland’s fishermen are already fraught thanks to Nicola Sturgeon’s fierce opposition to Brexit, which they hope will reinvigorate the industry.