More than 350,000 hectares of rainforest, twice the size of the Yorkshire Dales, is being chopped down to grow soy beans, most of which are genetically modified (GM).
The animal feed is then imported to British factory farms to produce cheap meat and dairy for supermarkets.
Friends of the Earth said that consumers are indirectly destroying the rainforest by buying meat and dairy and urged people to switch to a more vegetarian diet.
The charity pointed to new research by the Royal Agricultural College that found if just eight per cent of agricultural land in the UK was used to grow crops for animal feeds, it would be possible to halve the amount of feed currently imported from South America.
Sandra Bell, Senior Food Campaigner at FOE, blamed the drive to produce cheap meat for the growth in imported feed.
She urged the Government to support farmers in grazing more animals and growing animal feed themselves rather than relying on GM animal feed from abroad.
"Many people choose British milk and meat without realising that the animals in our farms munch on feed produced by destroying wildlife and rainforests in South America," she said.
"Animals should be born, bred and fed British - but pressure from supermarkets and biased EU subsidies force farmers to rely on damaging imports.
"The Government must listen to growing calls for it to restore a thriving meat and dairy sector by helping farmers switch to planet-friendly practices."
However farmers insisted imported animal feed is an essential part of producing affordable and nutritious meat and dairy in Britain.