Monsanto is the biggest company pushing for approval of genetically modified products around the world.

rBST (recombinant bovine somatotrophin/bovine growth hormone) was first approved in the US for commercial release in February 1994 by the Food and Drug Administration (FDA).

Critics have slammed the approval process as dubious. Michael Taylor, a corporate law officer, who joined the FDA as deputy commissioner for policy, enforced the approval of Monsanto's product to increase milk production.

He left the FDA to join Monsanto as director of regulatory affairs.

In its research presented to the FDA, Monsanto dismissed alarming changes in the test cows as "harmless physiological shifts".

The changes included major increases in the size of the cows' hearts, livers, kidneys, ovaries and adrenal glands.

In addition, not all the research done by Monsanto ended up in the hands of the FDA.

In fact, US government scientist Richard Burroughs revealed that cows which contracted udder infections and mastitis were often dropped from the study, thus skewing the results. It was later revealed that 9,500 cows from 500 farms contracted udder infections.

Burroughs was told he was "slowing down the approval process" and was fired after he asked for toxicology studies to be conducted on the hormone.

In addition, during the time Taylor was at the FDA, he ruled that milk from cows treated with the hormone should not be labelled as such. He also wrote guidelines that made it difficult for dairy producers to label their milk as "rBST-free".

Monsanto sued dairy farmers when they labelled their milk as "rBST-free".