The U.K. shouldn’t allow imports of food that fall short of the country’s own standards when it draws up trade agreements, the head of the National Farmers Union said.

Domestic production standards should be used as a benchmark in trade talks, NFU President Minette Batters said. Her comments signal that British farmers would face a setback if the government allows imports of products that are treated with certain chemicals or made using more lax animal-welfare rules.

After leaving the European Union last month, the U.K. is set to embark on talks with other nations to negotiate everything from food trade to data protection. The standard of products sold on supermarket shelves could be crucial for Britain’s agriculture industry because the country imports about half the food it consumes.

“This isn’t just about chlorinated chicken,” Batters said in a statement before her speech at the NFU’s annual conference in Birmingham on Tuesday. “This is about a wider principle. We must not tie the hands of British farmers to the highest rung of the standards ladder while waving through food imports which may not even reach the bottom rung.”

While the U.K. left the EU without crashing out, easing farmers’ immediate concerns about access to some markets, questions remain over how goods will flow across the border at the end of December. U.S. Agriculture Secretary Sonny Perdue last month hit out at Britain’s environment ministry over food safety rules, highlighting obstacles to a free-trade accord.

Trade uncertainty has weighed on U.K. farm sentiment, with one-year confidence falling to the third-lowest since 2010, the union said this month. Bouts of bad weather have added to the challenges. Relentless rain since autumn has kept farmers sidelined from fieldwork and curbed U.K. wheat plantings to the lowest in at least four decades.