Opening up Britain to US food imports under a ‘no-deal’ Brexit could have “serious” consequences for East Anglia’s hugely important poultry sector, farmers’ leaders have warned.

The National Farmers' Union (NFU) has joined the Unite union in saying it has "real concerns" after Zippy Duvall, head of the American Farm Bureau, told a British audience that a deal on chlorinated chicken would be an essential part of any transatlantic trade agreement.

NFU East Anglia adviser John Newton, who leads on regional poultry issues, said: "We've been clear that a no deal Brexit could have serious consequences for farms across East Anglia, including the region's hugely important poultry sector. It is also imperative that our standards are protected in any future trading arrangements.

"Our farmers produce around a quarter of the UK's meat chicken - about 250m birds a year - and the vast majority will be reared to Red Tractor assurance standards.

"There are real concerns our markets could be opened up to chicken produced to standards that are unacceptable here after Brexit, including chlorinated chicken from the United States.

"In a no deal scenario, poultry producers would also face supply chain disruption and potential labour shortages, threatening their ability to produce quality British food, and export taxes when selling chicken into the European Union."

A deal allowing a "smooth and orderly" exit from the EU was "vital", he added.

NFU deputy president Guy Smith said British farmers "will simply not be able to compete" against farmers operating to lower standards and such a deal would export UK production. "It would emaciate and be downsized - and not just farming, but the food processing industry," he said.

British farmers were proud of their high standards and simply lowering them to meet US ones would neither be acceptable to them, nor, he believed, to British consumers, he added. "The point is if you don't allow chlorine washes you demand a higher level of hygiene throughout the food chain."

Unite urged the government not to "sell out" British food workers. Chlorine washing, banned in the EU since 1997 over food safety concerns.

Unite's Bev Clarkson said: "We want a clear statement from Theresa Villiers, secretary of state for environment, food and rural affairs, that she will not sell out our food workers in any deal with Trump."