A $3 billion costing for New Zealand First's policy to remove GST from basic food was a mistake, Winston Peters has told Morning Report.

Watch the interview - part of RNZ's in-depth election series - here:

Mr Peters said his party's policies were costed at $10bn over seven or eight years.

Taking GST off basic food would be $600-700 million, he said, and the mention of $3bn on the party's website was a mistake by someone in his team.

"In fact I had a discussion with my team just about two days ago about correcting that," he said. "Parties make mistakes and in this case it's been corrected, it should have been corrected."

The party would leave it to a group of ordinary men and women to decide what foods would be considered basic, though Mr Peters said bread would be on the list, but chips and biscuits would not.

The cost of policies such as a 20 percent tax rate for export companies, and buying back shares in energy companies, would depend on the uptake or timing.

As in previous years, Mr Peters could be 'kingmaker' or 'queenmaker' if his party wins enough votes to make a coalition with National or Labour. He has said he would only make a coalition with Labour if he was told what the party's tax plans were. The party released its full tax plan this morning.

Mr Peters told Morning Report there was a "convention that in the first place you would go with the party with the highest votes" and talking first to the party that gained the most votes would be the "normal thing to do".

"But it depends who's prepared to talk to you," he said.

He said he'd never referred to bottom lines in terms of what he wanted from any post-election talks.

"My caucus colleagues, my board and my party is entitled to full consultation before somebody steps up like some dictator and says, 'I want this and I don't care you guys want.'

"I have never gone out talking about bottom lines."

Mr Peters said his vision was for dramatic economic change and a shift from "economic lunacy". New Zealand had gone down a path of economic revolution starting three decades ago while Australia, which had made incremental changes, now had greater growth and higher pay rates.

He said in order to implement the party's pledge of first-home buyers getting long-term low interest rates for up to 25 years, the government would have to be responsible for the scheme, not commercial banks.