Act leader David Seymour has slammed Prime Minister Bill English for suggesting Seymour regretted calling New Zealand First MP Richard Prosser a "f*****ing idiot."

And the insults directed at English are so personal they are likely to strain relations with the Act Party which relies on National for its survival.

Seymour suggested English and National were "toadying" to New Zealand First leader Winston Peters - who is likely to hold the balance of power after the election on current polling - to keep their ministerial

He questioned whether English had spent any time with voters recently.

Advertisement

"I do not regret my words and Act will not back down," Seymour said in a statement tonight.

"Has Bill English spent any time at all with voters recently? Because what I hear from angry constituents when I go door to door puts my language to shame.

"People are furious, not just about shifty Winston Peters, but a broken housing market and rising crime under both Labour and National."

English was questioned about Seymour's expletive on the campaign trail in Christchurch today and said: "I'm sure he regrets those comments and I would anticipate he's not making them again."

Seymour made the comments at a Business New Zealand conference in Wellington yesterday after Prosser said New Zealand First would nationalise ex state-owned energy company Contact Energy at its original share price.

The statement was later modified by New Zealand First leader Winston Peters who said the buyback of power companies would happen only when shares became available.

Seymour is Act's sole MP and holds the Epsom seat in an electoral accommodation with National, which is in turn supported by Act on confidence and supply. But Seymour is not a minister as other Act leaders have been and it gives him much greater freedom to criticise National.

His criticism is usually levelled at Finance Minister Steven Joyce but that has been extended to English.

Advertisement

"He's upset about a bad word? We're upset about the prospect of NZ First running our country's finances with retrograde 1950s policies.

"The supposed Kingmaker threatens to nationalise New Zealanders' savings and National's main concern is Act's language.

"National used to be a party of protecting property rights, and standing up for the individual against the government.

"Now they stand for toadying up to Winston Peters to keep their ministerial cars and salaries."

Bill English said he had no issue with Seymour.

"These sorts of comments are made in the pressure of an an election campaign," he said through a spokeswoman.