The Parliamentary Commissioner for the Environment has hit back at critics of her recent work on water quality, saying they need to face reality.
Last year the commissioner, Jan Wright, released a report warning the large scale conversion of land to dairying and the increasing number of cows will inevitably lead to deteriorating water quality due to increased nitrogen pressure.
The New Zealand Institute of Economic Research is the latest to dismiss the land use report.
In its paper looking at water and irrigation the economic think-tank suggested more needed to be done to understand the values communities place on water.
One of the authors, economist Bill Kaye-Blake, said they took into account the commissioner's report but felt it was outdated and not particularly relevant to their work.
"Look we know if we keep polluting the streams things are going to get worse. That's a very easy thing to say but it doesn't really help us out.
"What we did was, we said 'what policies could we put in place, how would those clean up the streams and what would they cost us'."
Dr Wright said the report was not simplistic or backward looking.
"It's actually looking forward til 2020, it's modelling the future very conservatively because one of the things I pride myself on in my job is not overstating environmental matters.
"But really the amount of nitrogen getting into our rivers and lakes is going to keep going up unless something changes dramatically."
Last year Fonterra chief executive Theo Spierings also dismissed the Commissioner's findings. "When you write a report about the past, it is looking backwards in my opinion," he said at the time. "If you take an assumption that we will grow dairy the way we have grown it in the last 20 years, you're right, but that's not my assumption."
Dr Wright said she had since written Mr Spierings a letter explaining what the report was about, and hoped he had read it.
"I would encourage people to read the report themselves ....it's simply about nitrogen pressure and the ongoing nitrogen pressure that's coming from the large-scale conversion we have going on.
"I know why the large scale land conversion is going on now, of course farmers need to make a buck, this is natural. But what is accompanying it is a whole lot more nitrogen and by denying it means we won't face up to it."