Post-Brexit tariffs on flour mean the price of bread in Ireland could rise by almost a 10th, a trade group warns.

Food Drink Ireland said because of rules of origin in the U.K.-European Union trade agreement, products containing more than 15% grain from the U.K. now face tariffs that raise the cost of the main bread ingredient by 50%.

Some 80% of the flour used in Irish bread is imported, mainly from across the Irish Sea after many millers closed down in recent years, leaving no industrial options on the island.

“This results in a distorted marketplace,” FDI director Paul Kelly said. U.K. or other euro-area bakers “using the same specification flour, but not facing the same tariff will be at a significant competitive advantage selling their finished product.”

The group is calling for a derogation on this regulation for the Irish bakery sector.