PORT makers in Portugal fear the effect of Brexit on its multimillion-pound export industry to the UK.

European Union laws ensure only the wine produced in the valley of the River Douro can be called port, and without this legislation, the UK could let in rival producers of fortified wines from the Commonwealth as part of post-Brexit trade deals.

For workers in Portugal, the EU’s name protection laws help ensure their livelihood by shielding them from industrial-scale, lower-cost copies. French champagne, Greek feta cheese and Italian Parma ham makers also benefit from the rules.

The United Kingdom is port wine’s second largest export market, valued at more than £40m, and Britain is yet to confirm whether it will keep the EU’s name protection rules after it leaves the bloc.

The United States has long fought against the laws, claiming they amount to trade barriers – an argument that is not lost on the UK Government as it eyes closer business ties with Washington.

Product name protection is not a minor issue – last week, the EU’s Brexit negotiator Michel Barnier singled it out as one of the three main outstanding questions, alongside a possible future border in Ireland and working out the post-Brexit EU/UK relationship.

The issue is likely to come up at an EU summit in Austria this week where leaders will assess the state of the Brexit talks.