Jacinda Ardern's modest rating for first 100 days as Prime Minister

Jacinda Ardern has rated her first 100 days as New Zealand's Prime Minister a 7 out of 10 in terms of productivity and promises kept.

On Newstalk ZB this morning, Mike Hosking asked Ardern to rate her first 100 days on the job with "10 being perfect and 1 being a disaster".

Ardern said she felt pretty positive about Labour and New Zealand First's month in power.

"The stuff we have said we would do, we have done," she said.

"I would give us a strong 7. I don't want to be a perfectionist."

Hosking laughed at the number, provoking Ardern to question his intent and press him to explain what the coalition parties had failed on.

Hosking said his laughter was not because of a presumptuous rating, but because he would have rated the success of the first 100 days much higher.

"I would have given you a 9.25 because you can't argue with the fact that you have done what you said you would do," he said.

"So you have marked yourself extremely harshly."

Ardern said her score was down to her perfectionist nature and not wanting to "sound arrogant".

During the early morning interview, the pair also spoke about Winston Peters' horse racing announcements made yesterday at the Karaka yearling sales.

"Her talked about the fact that in our racing industry we have rising costs and diminishing returns," Ardern said.

Newstalk ZB host Mike Hosking suggested the coalition parties deserved a higher rating than 7 out of 10.

"Twelve years ago, back when he was working alongside the last Labour government, he developed a tax regime that assisted particularly with bloodstock and he is looking again at that area. That is something we are working with the minister of finance and revenue on.

"The second issue he is working on is an all-weather track because if rain or weather causes the cancellation, there is significant cost to the industry."

Ardern said they were committed to working more constructively with the industry than had been seen in the past nine years, but it was all subject to budget bids.

Hosking questioned Ardern on whether the tax breaks would be any different, bigger or better than tax breaks for any other industry.

Ardern pointed out tax breaks for the racing industry had existed before, but had deteriorated over time.

"What was originally put in place has eroded, so it is about going back and seeing whether we can make that more workable again," she said.

Hosking also questioned why the coalition parties were favouring the racing industry over others.

"In areas where we are relative to other international industries, if there comes disincentive to invest in your domestic industry and more in incentive to invest overseas, then you have to look at your competitiveness," Ardern said.

"We have looked at that for forestry and the film industry for instance, and this is an area where it looks like the same thing is happening."

Incentives were made by looking at whether there was enough of a benefit overall to the New Zealand economy and whether the economic benefit outweighed the economic cost.

Ardern and Hosking also discussed Donald Trump's views on the TPP, the rejection of a "work for the dole" scheme, and Manus Island refugees.