Britain and the European Union are set to go head-to-head over disputed fishing rights in the first legal row over trade since leaving the bloc.
The UK has banned European ships from catching sand eels, a food of choice for British seabirds, to protect wildlife.
Brussels has challenged the move, arguing it breaches the post-Brexit trade deal and will discriminate against Danish fishing vessels.
The issue will now be heard at a three-day tribunal hearing after formal talks failed to resolve the impasse.
A panel of three mutually agreed international judges will hear the dispute at a court in The Hague from next Tuesday.
They will have the opportunity to either uphold Britain's position, demand a change or order Britain to withdraw the ban altogether.
The EU could retaliate with tariffs on British exports if ministers refuse to comply with the ruling.
The fishing rights issue will be heard at a tribunal hearing next week
Britain has banned European ships from catching the sand eel (photo, eaten by a puffin)
The Permanent Court of Arbitration is due to rule by the end of April, although it could make a decision earlier.
Neither party has the right to appeal if they disagree with the verdict.
Under the existing trade agreement, sandeel is a jointly managed fish stock.
Unlike fish, it is not caught for food in Britain or across Europe, but is eaten by seabirds such as puffins and other fish such as cod.
Rishi Sunak's government last year banned all vessels from catching the fish in English waters in a bid to help conserve endangered species.
A similar move was adopted by the Scottish Government.
Britain is currently preparing to negotiate with the bloc over catch limits to be agreed before the current arrangements expire in June next year.
Last month it was reported that the EU would urge Britain to follow the jurisdiction of the European Court of Justice in return for their agreement on a new deal.
The tough position was set out in a document seen by The Times and presented to a council of European ministers.
It made clear that Brussels would demand important concessions in the areas of fisheries, the European Court of Justice and youth mobility.
Gannet, classified as a protected species in Britain and under the EU Directive
A sand eel, also called sand lance, pictured on a beach in the Netherlands, undated
Charles Clover of the Blue Marine Foundation said the measures leave British fishing waters at the mercy of 'French trawlers', adding that the demands are 'absolutely outrageous'.
The document states that Britain must also comply with rulings by the European Court of Justice on EU law.
Charles Grant of the Center for European Reform said: 'It would set a precedent for much closer cooperation in a range of other areas, such as energy.'
He added that it will be difficult for the Prime Minister to meet the demands because the reset “could anger the Conservatives and the Reformists.”
