National Party MP Simon Bridges admits to a "bit of dejection" after giving up on his leadership hopes on Tuesday, but said he had bounced back and was looking forward to working under leader Chris Luxon as finance spokesman.

Bridges has given his first interviews since he withdrew from National's leadership contest, leaving it to Chris Luxon to take uncontested. On Friday, Luxon announced Bridges would get the sought-after finance and infrastructure portfolios and the 3rd ranking in his shadow Cabinet.

Bridges said it was a week of "ups and downs."

"I'd be lying if I said there wasn't a wee bit of dejection there for a while, but what made the medicine go down better is that I have a lot of respect and time for Chris Luxon. I think he's a guy that commands that, actually.

"So that made it a little less difficult and I could see actually we have the ability to get ourselves back to where we have been in the past, which is unified and focused."

He said there was an advantage in Luxon coming into politics without any political baggage.

"It means you see things with fresh eyes. I like that in our leadership team, there is that blend of his outside experience and leadership and organisational skills, but also someone like me with Parliamentary and ministerial experience, and also maybe some street smarts. I think it's going to work really well."

Bridges had a lot less to say about Judith Collins, whose attempt to demote Bridges resulted in caucus passing a no-confidence motion in her last Thursday.

Luxon has said he will give Collins a good role in his line-up. Asked if he believed Collins should stay, Bridges said "that's absolutely the leader's prerogative."

"That's possibly the benefit of fresh eyes. I'm in the space of letting bygones be bygones, and thinking about the future."

He would not say more.

Bridges said he was excited about his own move to the finance portfolio, and hoped to rebuild National's credibility in those areas.

"National is at its best when it is doing a strong job in these areas. We have been the most trusted party on these issues before, and we can get back there."

Bridges also had to contend with his son being hospitalised after a playground accident at school.

Luxon had travelled to Tauranga to announce Bridges as his finance spokesman, but Bridges had to pull out after his son, Harry, had a bad accident on a swing an hour beforehand and was taken to hospital.

Bridges said Harry, 7, was going to be fine but had torn his liver and the internal bleeding meant he had to be taken to Starship Hospital in Auckland. He was expected to be there for a few days but would hopefully avoid surgery.

"Livers, I'm told, are amazing at healing themselves and it seems it's going to do that so he won't need an operation. We are hugely grateful for everything the staff are doing there, they're amazing, and the staff at Tauranga Hospital before that."

"Harry has come out alright, which is the most important thing."

On old rivalries

Luxon's lineup includes his deputy Nicola Willis and Chris Bishop, who is also tipped to get the 4th ranking. Both are from the party's liberal side, while Bridges is more conservative, and both were also involved in Todd Muller's successful coup against Bridges in 2020.

Despite that history, Bridges was confident they would work together well.

"I think what we all realise is that now is the time to put the past in the past, and focus on the future. Where there have been disagreements in the past, they've been around policy and ideas.

"And that's actually really important and I hope it continues, because that will make a stronger National Party. National is at its best when it is a liberal–conservative party, and the blending of that and talent is what I know Chris wants to do with his reshuffle."

On the finance role

He will return to Parliament on Tuesday to face off against Finance Minister Grant Robertson – who said he intended to treat Bridges "with the same respect that I have the other five National Finance people I've dealt with".

Bridges laughed when told of Robertson's response and said it was "very subtle of him".

"But I have a feeling I might be in the role a bit longer, and he's up for a run for his money. Or, more accurately, New Zealanders' money."

"I don't think people should be expecting fireworks from day one, even though I have a reputation for that.

"New Zealanders deserve us to be an honest explainer of what's going on in the economy, not just carping from the sidelines but over the next year or so I'll bring some big solutions to the longer-term problems we've got like productivity, debt, inflation and businesses with a whole lot of trouble at the moment in restrictive Covid settings."

He believed he had served a good apprenticeship for the role, pointing to his role in economic and infrastructure related portfolios under the Key government. Those included transport, economic development and energy and resources.

He would also be talking to former finance ministers – such as Bill English and Steven Joyce – for advice, as well as talking to economists and others in the sector.