The Soil Association has accused the BRC of being "rude" and "arrogant" for claiming consumers don't want to know if their food has come from animals fed with GM maize or soya.
Policy director Peter Melchett challenged BRC head of media and campaigns, Richard Dodd, to support his "ludicrous" position on the issue.
"There is overwhelming evidence that consumers do want to know whether animals were fed on GM feed," said Melchett. "EU polls have shown this. For the BRC to say otherwise is insulting to consumers.
"I challenge it to produce one shred of evidence to support its ludicrous position. I don't think a single supermarket would have dared to say what the BRC has said."
Dodd was reacting to a Soil Association report that claimed most cattle and pigs in Britain were being fed with GM feed.
Silent Invasion - the hidden use of GM animal feed in the UK, suggested about 60% of maize and 30% of soya fed to dairy cattle and pigs was GM.
It claimed that the public was unaware elements could end up in meat and dairy products and called for food labelling to reflect the fact.
"The law doesn't require the sort of labelling the Soil Association is calling for, and there is no basis in science to justify this kind of labelling because there is no evidence of transference, so there is no risk whatsoever to customers," Dodd said.
"I don't think there is any demand from customers for this information. There is a danger customers would be unnecessarily worried if there were GM labelling, because you can't expect customers to study the science or have any detailed knowledge of this issue."
Melchett refuted the BRC's comments, and claimed peer-reviewed science supported the theory that DNA from GM feed entered the food chain.
Farmers blast BRC p50