LONDON (Reuters) - Consumers are unwittingly eating food produced from genetically modified crops with nearly all milk, dairy products and pork produced from GMO-fed animals, the country's largest organic certification body said on Friday.

The Soil Association, which opposes GMO crops, said that a survey estimated about 60 percent of maize and 30 percent of soya fed to dairy cattle and pigs is genetically modified.

"Biotechnology companies have clearly used imported animal feed as a Trojan Horse to introduce GM into the UK food chain," Soil Association director Patrick Holden said in a statement.

There has been significant opposition to GMO crops among British consumers.

The Soil Association, which certifies about 70 percent of the organic food sold in Britain, said there was no requirement to label foods produced from GMO-fed animals so shoppers found it hard to avoid these products.

Poultry producers have widely adopted non-GMO feed policies, in contrast to dairy and pig sectors, but around one-third of eggs are from GMO-fed hens, the Soil Association said.

(Reporting by Nigel Hunt; Editing by Peter Blackburn)