A post-Brexit trade deal with the US could see a massive increase in the amount of cancer-causing toxins in British milk and baby food, The Independent can reveal.

American regulations allow more than 20 times the quantity of harmful aflatoxins in food products, compared to the stricter regime imposed by the European Union.

US standards also allow products made with nuts and cereals to have higher levels of the carcinogens, which cause damage to DNA and make cells more prone to becoming cancerous.

While a direct link to liver cancer is widely accepted, the lower US standards allow American manufacturers to produce food more cheaply.

Critics are now warning that ministers pursuing a quick trade deal with Washington would be putting GDP growth ahead of public health if safety standards are weakened.

It follows a major furore over whether chlorinated chicken would flood the UK market, if a future trade deal allowed products to be sold in the UK but regulated by a more lenient American regime.

US regulations permit 0.5 micrograms per kg of aflatoxins in milk, cereals, nuts and dried fruits, but the EU restricts levels to 0.025 micrograms – twenty times lower.

In all milk and dairy products, EU limits are ten times lower at 0.05 micrograms per kg.

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Simon Dawson, a lecturer in Food Science and Techonology at Cardiff Metropolitan University, told The Independent: “Exposure [to aflatoxins] can have a number of detrimental effects on the body; therefore, levels should be kept as low as reasonably achievable due to their genotoxic and carcinogenic effects.

“With babies and infants, their immune systems are not fully developed therefore toxins such as these can affect their bodies more so than how an adult would react.”

The chemicals are produced by fungi found on agricultural crops such as maize, peanuts and tree nuts, and can contaminate crops in the field, at harvest and during storage.

People are exposed by eating contaminated products or consuming meat or dairy foods from animals that ate contaminated feed. Studies have shown a direct linked to liver cancer, as the toxins damage genes which suppress the growth of deadly tumours.

Mr Dawson said: “Aflatoxins primarily attack the liver. Large doses will lead to severe illness and death, usually through liver cirrhosis.

“Chronic low doses have both an immunological and nutritional effect on the body as they are classified as being genotoxic carcinogens. Studies have shown changes to behaviour, decreased nutrient digestion and absorption, reduced growth rate, risks of cancer and a range of other nasty effects.”

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He said that there were no studies he is aware of that show a level of 0.5 micrograms per kg resulting in adverse effects, but added: “Having said that, we should be aiming to produce foods with as low as reasonably achievable levels of aflatoxins, therefore importing products with levels that exceed EU legislation doesn’t feel like we are making positive steps.”

Unlike the EU, the US does not have a specific tighter limit on aflatoxins for babies and infant formula milk.

Brussels set its limits in 2006 taking into account extensive research and best available practice to detect the chemicals, which is continuously reviewed and updated – but the US standard has not been updated since 1977.

Since then, there have been incidents in Africa and Asia involving intense contaminations of aflatoxins, including one in Kenya in 2004 which claimed 124 lives.

Maize can carry the harmful aflatoxins (Getty)

American standards are not considered unsafe, but the more generous limits are part of the reason US farms can produce cereals more cheaply, and were a significant obstacle in the eventual breakdown of trade talks between the EU and US.

The Food Standards Agency told The Independent that the lower EU levels currently adhered to in the UK are there to help “protect public health”.

A spokesman said: “The methods and criteria used to assess risk in the US are different to those used in Europe and the UK.

“The maximum levels of aflatoxins allowed in foods is agreed upon at a European level on the basis of sound scientific evidence, and the levels in food are kept as low as possible in order to protect public health.”

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He added that the lower limits remove the most contaminated products from the food chain and ensure food businesses apply stronger agricultural and manufacturing practices.

A spokesperson for the Department of International Trade said: “We are committed to a mutually beneficial economic arrangement with the US but are clear that we are not going to dilute our high food safety standards or our high environmental standards in pursuit of any trade deal.

“Discussions with the US about our future trading relationship are at a very early stage and it’s too early to say what exactly will be covered in a future agreement.”

Cereals would undoubtedly form a major part of the agricultural aspects of any US/UK trade deal, with cheaper, lower production standards at risk of undercutting British manufacturers in much the same way as chlorine-washed chickens allows US farmers to deploy more intense production methods.

Labour’s Shadow International Trade Secretary Barry Gardiner said: “We in the Labour Party have been absolutely clear that any trade agreement we come to with any country must not reduce the safety standards or animal welfare standards that we have already got in the UK.

“We have been asking the Government for many months for clarity on this, and we have been receiving confusing messages.”

Ian Murray MP, a leading figure in the campaign group Open Britain, said: "The Government’s desperation to do a trade deal with Trump’s America could put the health of British children and babies at risk.