The number of chemicals applied to supermarket vegetable crops 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 applied to onions, leeks, wheat and potatoes has been steadily increasing since the 1960s.

This is despite industry data showing that the weight of pesticides applied in the UK 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.

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