'It is hard to walk away' - National MP Steven Joyce

National Party stalwart Steven Joyce is clocking out after nearly a decade in politics, saying there were good days and tough days and "interesting international headlines".

"People will look back in about five minutes and say 'Steven who?'" he told media after announcing his resignation on Tuesday afternoon.

He was a high-ranking Minister during the three-term National government, chaired five election campaigns, and was Finance Minister leading into the election.

When Simon Bridges took over as National leader last week, Mr Joyce was not offered the coveted finance portfolio.

He's adamant that's not behind his decision to retire from politics, and instead it's a decision about his own future and an opportunity for the National Party to refresh itself for 2020.

"Simon has been very generous, he offered me a front bench position, and a choice of portfolios," he explained.

"I'm not even sure if I was offered finance I would have necessarily stayed for two-and-a-half years."

He said there was no bitterness involved in his decision to call it quits.

"If I was in a petulant mood I'd probably go to the back benches, grow a beard and just sit there fuming for a while."

Mr Joyce leaves Parliament after seeing his party fail to form a Government after the election, and after his own failure to win the leadership. But he doesn't see it as failure.

"The thing about politics is you have to take the rough with the smooth... you can never bat 100 in politics."

He'll leave Parliament defending his $11.7 billion hole claim, which drew fierce criticism during the 2017 election campaign, saying he absolutely does not regret it.

"That's one of the many things that this Government is going to struggle with, is how tight they've set themselves up fiscally over the next couple of years."

He is "conscious and confident that Simon and his team will take them to bits over the next two-and-a-half years".

Mr Joyce plans a return to the commercial world, he's ruled out going back to radio, but has expressed interested in the technology sector.

One of his most proud accomplishments as a politician is setting up ultra-fast broadband, he says, dubbing it "the infrastructure for the 21st century".

"The whole thing has been an absolute blast and an absolute privilege, to be blunt," he said.

"You have good days and bad days - and there's tough days - but a day you're serving your fellow New Zealanders and getting that opportunity to help them in whatever happens is actually a pretty cool thing.

"It is hard to walk away from."

He couldn't sum up his political career in one word, but opted for a sentence: "I like to get on and get things done".