Primary Industries Minister David Carter has criticised the analysis by Manawatu Whanganui Regional Council on the economic impact that its One Plan will have on farming and horticulture.
He's promising changes to the Resource Management Act to tighten that requirement.
Mr Carter raised his concerns following memos from his ministry outlining the implications of a recent Environment Court decision rejecting appeals against the regional plan.
The Court backed a proposal to impose nutrient caps on intensive farming and vegetable growing operations to protect waterways from nitrogen pollution.
Memos to the minister include details of economic impact modelling done by Landcare Research.
A case study for the Manawatu catchment indicates farm profits could fall by 22% to 43% as a result of land use changes needed to meet water quality targets in the plan.
Mr Carter said he will wait for the outcome of High Court appeals from farming and horticulture bodies against the Environment Court ruling, but he's concerned about the restrictions proposed in the One Plan.
Federated Farmers says it will be challenge the regional council's cost-benefit analysis under the Resource Management Act.
chief executive Conor English says the impact would go well beyond farming, causing income cuts and job losses right through the supply chain.