The National Party denies exaggerating the impact of Labour's proposed water tax on farmers, even though industry body Dairy New Zealand's figures show just one in six farms would be affected.
Party leader Bill English and finance spokesperson Steven Joyce have told farmers the tax could cost $50,000 to $100,000 per farm.
Labour said that was scaremongering and should be silenced by the figures supplied to RNZ by DairyNZ.
Read RNZ's examination of the water-tax numbers in its Fact or Fiction series.
Speaking on the campaign trail in Rotorua, National's leader Bill English denied he had been over-egging the impact of Labour's proposed tax on the rural sector, which would impose a levy on commercial water use at one or two cents per 1000 litres.
"We've talked about the farming community being affected by a range of these proposed taxes ... the water tax which impacts heavily on those who use a lot of water.
"There's also a big horticulture sector that's a big commercial user of water.
Labour's proposed water tax frequently featured in Mr English's addresses to rural communities he has visited during the campaign.
He said he was not trying to play urban and rural voters off against each other, but was merely laying out the facts - including that there has been intensive work on water quality for five or six years.
"Other political parties have picked it up as a kind of wedge issue where they think they can punish a small group either with taxes or in the Greens case just kill the cows off."
Labour's David Parker said his party was not trying to create an urban/rural divide, but the aim was to target the source of water pollution.
"The problem with our polluted rivers is predominantly in rural areas, Mr Parker said.
"It is true that urban areas need to do better but it's also true that in recent decades cities and towns have spent money on cleaning up their sewerage and factory outfalls.
"And so at a time when rural rivers have been getting dirtier, city waterways have been getting cleaner."
The assertion the Greens want to kill off the cows in New Zealand was preposterous, its leader, James Shaw, said.
"My first response was to laugh out loud - it's desperate, scaremongering hyperbole from an outgoing administration that's grasping at straws."
Mr Shaw said it was his view that National was the one which has been fomenting the disagreement between voters in the city and those in the provinces.
"In order to try and shore up its rural base, particularly against the threat from New Zealand First."