Newshub can reveal yet another likely price of getting a coaltion deal with New Zealand First - free-to-air sport.

In a previously unaired interview, Winston Peters promised the policy would be a "non-negotiable" in return for his support in Government.

While the monarch-maker is staying quiet on what he'll press for in coalition talks, a previously unaired interview with Mr Peters at the Karaka sales in January this year suggests free-to-air sport is likely to be a non-negotiable demand.

Mr Peters insisted the policy would be implemented and said he didn't make promises he couldn't keep.

"I'm not going to say we're going to try and implement it - we will implement it," Mr Peters told Newshub.

"The fact is we don't go around making promises that we don't keep.

"There's about 1.2 million people who can't afford Sky. They're the mothers and fathers who put kids on sports fields all around this country."

When asked whether the policy was a bottom line, Mr Peters said he wasn't talking about bottom lines, but would stick to his word.

"Everybody who's dealing with Winston Peters and NZ First knows we intend, as in the past, to keep our word, so they should stop humbugging around."

Mr Peters is a sports lover from way back. He even put on a "media manager" hat, so he could be part of 2015's Parliamentary Rugby World Cup.

While the Parliamentary Cup doesn't make the cut for the NZ First's 'Games of National Significance' broadcasting policy, the actual Rugby World Cup would, along with domestic rugby tests, all 'significant' cricket, netball, soccer, tennis, basketball and rugby league matches, both the summer and winter Olympics, the Commonwealth Games and, of course, the NZ Trots.

The obvious catch is that sports like rugby may not be able to sell broadcast rights for as much and would have less income to pay players.

New Zealand First put up a private member's Bill on the policy this year, but it was voted down by both National and Labour.

"No Government is going to take roughly $125 million - the sporting rights income - away from sports in New Zealand," said Labour's spokesperson for sport and recreation Trevor Mallard at the time

But despite their earlier opposition, neither Labour or National would rule it out today.

Sky TV issued a statement warning of the costs involved in producing live sport and of the funding sports would miss out on if competition for rights was taken away.

Newshub.