HOW WE ( The Daily Mail) CARRIED OUT THE TESTS

Our researchers bought 20 items from Tesco and Sainsbury’s, Kwik Save and Holland & Barrett .

The products were sent to the Central Scientific Laboratory, an agency of the Ministry of Agriculture, in Norwich, which has developed its own testing procedure to establish whether the fingerprint of Roundup Ready soya is present. It also has a test for the genetically modified Bt maize.

The soya has been modified with genes from the petunia and soil bacteria to make it resistant to Monsanto’s weedkiller Roundup. The genetic modification leaves a DNA fingerprint within the soya which can be identified in tests known as PCR - Polymerase chain reaction.

All the samples were analysed in duplicate to make sure the results were confirmed.

The soya DNA is pulled out of the sample using a buffer solution of chemicals. Samples are treated with chloroform to remove the fat, with isopropanol to separate out the DNA and ethanol to clean it up. The testers create thousands of copies of the soya DNA, which allows them to be sure whether it is GM or not.

In three of the four cases this ‘amplification’ process worked well. Amplification was poor with the So Good soya milk, however the CSL team were still confident it included traces of GM.