Prime Minister elect Christopher Luxon may be the one responsible for lengthening the time it's taking for government coalition talks to conclude, as he fights tooth and nail to get his tax policies over the line, a political expert believes.

It's been reported there are a maximum of three issues left to be resolved between National, Act and New Zealand First but Luxon believes he will be in Auckland for the next few days as negotiations drag on.

One of the issues widely reported to be of contention is National's plan to provide tax cuts for middle-income New Zealanders, the central policy that much of the country will have elected the party for.

Newstalk ZB political editor Jason Walls told The Mike Hosking Breakfast on Monday there's trouble if one of the challenges of discussion is around tax.

"If that is a sticking point then the Nats have a lot to answer for," he said.

"They really campaigned on this tax cut policy and if they can't deliver on that then they're in for a real lot of explaining to do to the New Zealand public - who elected them on the basis they were getting tax cuts."

Hosking agreed, asking if such an action would alienate the party from being trusted by the nation.

Walls said he believed National's fear of losing the public's trust, due to how much they'd promised around the cuts, was the reason why coalition talks were continuing to drag on.

"If Winston is playing hardball, then Luxon is playing hardball back, because he knows he can't turn around and say 'Sorry guys, we can't get it over the line with Winston but we got something else instead'," he said.

"New Zealanders won't settle for a second-rate tax policy."

A lot of National's reputation rides on getting the tax policies over the line. National's incoming finance minister, Nicola Willis, told TVNZ’s Breakfast she would resign if a National-led government couldn’t deliver on the tax cuts it’s promising.

"I would resign because we are making a commitment to the New Zealand people and we intend to keep it," she said at the time when pushed about whether the foreign buyers’ tax would work.

When asked about when a coalition deal would likely be completed at this rate, Walls stood firm on his belief that an end-of-week result would be most likely.

"Tentatively, I'd say Thursday - flying down for Friday to have something stitched up for the weekend."