The number of chemicals on UK supermarket vegetables has increased by up to 17 fold in 40 years, data shows, as the organic food industry and scientists have warned that consumers are exposed to a "toxic cocktail" of pesticides.

Figures released for the first time by the Soil Association, which certifies organic food, show the number of toxic chemicals found in onions, leeks, wheat and potatoes has been steadily increasing since the 1960s.

This is despite industry data showing that the volume of pesticides found on supermarket vegetables has halved since the 1990s.

Speaking at a Royal Society of Medicine conference on pesticides yesterday, where the figures were unveiled, scientists warned that consuming tiny amounts of many different chemicals on a regular basis could be harmful to human health.

Consumers are being exposed to
Consumers are being exposed to "toxic cocktail" of pesticides, scientists have warned. Photo / Getty

Consumption of "toxic cocktails" of low levels of pesticide cocktails are thought to be linked with degenerative diseases like strokes, heart attacks and cancers.

Speaking at the conference, Prof Anne Marie Vinggaard, division of diet, disease prevention and toxicology, at the National Food Institute, said: "Chemicals can have a mixture effect. They may have no effect by themselves but when mixed have a pronounced mixture effect.

"We are not just exposed to pesticides. We are exposed to a lot of chemicals acting together and we must take account of this cocktail effect affecting the same target audience that the pesticides are."

The figures were compiled by data firm Fera Science, which used to be a Government arm, and were only made public after the Soil Association paid for them to be released from archives.

Onions and leeks have seen the biggest rise in toxic chemicals applied to them with the number rising 17 fold from 1.8 in 1966 to 32.6 in 2015, the data showed.

Back in 1974 less than two chemicals were applied to an average wheat crop, a figure which rose more than ten fold to 20.7 in 2014.

And potato crops are now sprayed with five times more chemicals than they were in 1975 with the number rising from 5.3 to 30.8 in 2014.

It comes after a chief scientific adviser to the UK government recently warned that the assumption by regulators around the world that it is safe to use pesticides at industrial scales across landscapes is false.

Dr Michael Antoniou, head of the gene expression and therapy research group at King's College London, added: "All this evidence shows that you should minimise your exposure to pesticides.

Minimally as a precaution you should minimise your exposure to pesticides. The only way to guarantee that, is by eating organically"

"A long term study of roundup in rats found that the lowest dosage, that was 75,000 times below the recommended dose of glyphosate [a common crop weed killer] had Anatomical Level toxicity leading to fatty tissue liver disease.

Keith Tyrell, spokesman at the Pesticide Action Network UK, said: "There is a huge lack of transparency there and it undermines the public trust in the regulatory system."

"It should be up to the pesticide companies to prove that the pesticide does not cause harm, not up to the researchers to show that there is harm."