Intensive dairy farming and nitrate-laden fertiliser are contaminating the Canterbury water supply, says Fish & Game New Zealand.
It is calling for no more cows to be allowed on the Canterbury plains and for the use of fertiliser to be regulated and reduced.
The group tested 114 drinking water samples from the Canterbury plains and found that over half of them were above the trigger level for increased risk of bowel cancer.
"We used Mike Joy from Victoria University and he's got a machine that measures nitrates, and that's what we did," Fish & Game chief executive Martin Taylor told Morning Report.
"We compared [the figures] to some of the data that Environment Canterbury and the Council had found and it's entirely consistent with what we know is happening on the Canterbury plains, so it's nothing new."
However, Federated Farmers have slammed the research, calling it a beat up.
Mr Taylor said that was not the case.
"All we've done is some testing so if they want to think it's a beat up, I put the challenge out to them to drive round the Canterbury plains with us, and do some testing with us and see whether they think the results are a beat up or not," he said.
"Federated Farmers probably need to get on board instead of denying that it's an issue... and try and find some solutions."
Mr Taylor said one solution could be to have a cow-pad attached to an effluent system, which would capture a lot of the animal contaminants seeping into the groundwater.
"But the main thing is just not to spray Urea [fertiliser] around and then irrigate the hell out of the land just to force grass growth."
He said Fish & Game wanted to keep the problem at the forefront of people's minds - especially because it was no longer just an environmental issue.
"This is now a human health issue and what we've got to do is say 'look, it's not right that an industry can contaminate our drinking water and that they can get away with it'," he said.
"We've got to bring in some action so the government has to make some changes to the National Policy Statement on Freshwater, and have absolute bottom lines on nitrates, farmers need to accept that they don't just need to spray around and irrigate and leech it all into the surface water, which goes into the ground water."
"We've got to have a full solution."