Federated Farmers is calling the animal advocacy group SAFE a group of "vegan fundamentalists" after the publication of drone footage of feedlots in South Canterbury.
Yesterday Safe called for the government to block feedlots saying it showed overcrowded cattle after the footage aired on Radio New Zealand's Checkpoint.
However, Federated Farmers said Safe did not really care about animal welfare and said their goal was to end all animal farming.
"Safe's agenda is to get rid of farmed animals. Animal welfare is a secondary concern for them," Miles Anderson, Federated Farmers meat and wool chairman, told RNZ.
"They are vegan fundamentalists. I take most of what they say with a grain of salt. It would do them a world of good to have a nice leg of lamb."
The footage showed the Five Star Beef Limited feedlot in Ashburton, New Zealand's biggest feedlot which has been running since 1991.
The cattle spend six months grazing, eating grass, before being moved to the feedlot where they are locked in square, uncovered pens, given vaccination to prevent disease and fed grains, for anywhere from two-and-a-half, to eight months.
Minister of Agriculture Damien O'Connor also launched a scathing attack, saying New Zealand would be crippled if it listened to everything Safe said.
Mr O'Connor said the Five Star feedlot had been around for a long time.
"For the most part it has been very well managed. There have not been issues to date," he said.
"Clearly it is not the mainstream type of production for New Zealand. But we are open to innovative ways to produce good quality beef. This is one of them.
"Clearly the image of pastoral farming is the one New Zealand promotes and it is the mainstay of our industry."
He said Safe had to "live in the real world".
"We appreciate their views but New Zealand would be crippled if we listened to everything they said."
Safe told Checkpoint it had serious concerns about both animal welfare and the environmental impact of having nearly 20,000 cattle confined.
"The farmers who are doing this are just wanting to make a quick buck by putting the animals in these sorts of feedlots and it's putting our international reputation at risk," said Marianne Macdonald, Safe head of campaigns.
"They've got no shelter from the blazing hot sun or from the freezing winter temperatures, they're just there, in those barren pens."
Feedlots are contained pens with cattle fed from crops which have been grown elsewhere.
They are used either to give beef a particular taste for specialised markets or to spare paddocks wear and tear elsewhere on the farm.
