Fears about chlorinated chicken in UK shops after Brexit have been dismissed by a US food official – as he revealed poultry is now being washed in acetic acid instead.

American food safety standards are “more advanced and more modern” than the “old-fashioned” EU approach, Ken Isley of the US Department of Agriculture insisted, in a combative interview.

Criticism has grown in the UK that ministers will bow to US pressure to accept chlorine-washed chicken if Britain does leave the EU, in their desperation for a trade deal with Washington.

Now Mr Isley has condemned “myths”, adding: “I think the concerns and fear are unfounded. I would stack US food safety and our food safety record against anywhere in the world.

“Chlorinated chicken is an example. That practice and processing is very, very limited in the US now and is being phased out, not for food safety reasons, but because newer technologies become available.”

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Asked, ahead of a food convention in Chicago, what new technology exists, he replied: “There’s acetic acid, is one of them.”

Attacking practices in the EU, food official added: “In a lot of ways, it [the EU approach] is old-fashioned, it’s based on traditions, not based on modern science and technology.”

The comments were quickly criticised by the consumer group Which?, highlighting how “foodborne disease in the US is around 10 times higher than in Britain”.

“The problem with chlorinated chicken and similar treatments is that they are too often used as a desperate attempt to make up for widespread safety problems in the US food production process, which can leave bacteria like salmonella to run rampant,” said Caroline Normand, its director of policy.

“Brexit is an opportunity to design a joined up food and farming policy that ensures food is produced to the highest standards – the nation’s health needs must not be used as a bargaining chip that could be given away to facilitate trade.”

The row follows the publication of the US’s “negotiating objectives”, which would remove barriers on “sanitary and phytosanitary” standards – in order to sell chlorine-washed chicken and hormone-pumped beef, critics said.

Last week, Mr Fox said: “There’s been no argument about food safety on chlorine-washed chicken – it’s been an argument about animal welfare,” he told an event.

“So, it’s not been about food standards per se, so that’s a slightly different debate and much more difficult to quantify because the legal definitions about it at the WTO are much less.”