The first parliamentary showdown between Christopher Luxon's new-look National Party and Jacinda Ardern's Labour Government did not disappoint.

It was Luxon's first go at firing questions at Jacinda Ardern - and he nearly lost it when asking her about the lack of ICU beds.

He stammered his way through a question, appearing to lose his place and apologising before managing to get it out.

Ardern deftly rejected the question's premise, saying the last Budget provided funding for new beds.

National picked good targets during Question Time, Herald reporter Thomas Coughlan said: ICU non-delivery and inflation.

MPs kept up the pressure, but failed to land a killer blow - and the PM handled Luxon's ICU question expertly, focusing on preventing the need for intensive care.

National decided to use the five questions it had to give each of its top MPs one question each.

Another highlight was the exchange between Finance Minister Grant Robertson and National's Simon Bridges, with Robertson responding to a question on the Government's earlier predictions over Aotearoa's economic recovery by subtly pointing out how "quickly numbers can change" - a quip directed at Bridges' recent move up the National caucus ranks after the removal of Judith Collins as opposition leader.

Labour and National have did not wait until Parliament resumed sitting this afternoon to lock horns.

Earlier, the day began with some friendly fire, when Luxon U-turned on remarks from Bridges about the Reserve Bank, saying National's position was not yet that Governor Adrian Orr should leave when his term ends in 2023.

Grant Robertson sniped at Luxon's economic strategy as he headed into caucus, saying Luxon needed to find his way out of National's fiscal "Bermuda triangle".

"I've heard often from National Party members that they want to spend more money. I've also heard that they want to cut taxes, and I've also heard that they want to cut debt.

"Mr Luxon's policy continues to be stuck in that fiscal Bermuda triangle and he will have to find his way out of that," Robertson said.

Luxon said Robertson was trying to "lecture" Bridges, ahead of their clash today.

"Look, Grant Robertson trying to lecture Simon Bridges or myself for that matter on the economy is something I won't listen too closely to," Luxon said.

"Our issue is simple, we think there has been a tremendous amount of wasteful spending. That therefore means we're taking on higher levels of debt. That means we don't have the capacity, fundamentally to invest in the economy in the way we want," Luxon said.

Bridges himself got in on the action.

"We've got a sense that Grant Robertson and Labour are overcooking it [the economy].

"I respect Grant and I think it will be a good contest," Bridges said.

Luxon said he was "relaxed" about his first Question Time clash as Leader of the Opposition today.

"For me it's an opportunity to prosecute the case with the Government on non-delivery.

"We followed the normal routine that we have for preparing for questions - there's been no extra study needed per se," Luxon said.

On the economy, Luxon would not put his finger on just how much or how little spending he would like from the Government. Usually, Government spending hovers at just under 30 per cent of GDP, although it tends to rise during an economic downturn when government spending increases and the economy shrinks.

In 2019, core government spending was 28.7 per cent of GDP, it is now 34.4 per cent of GDP, and expected to drop back down to 29.2 per cent by 2025, according to the Treasury.

In the last year of the previous National Government core spending was 27.8 per cent of GDP.

"The difference in our assumption is we're looking at things in the macro always and you've got to be able to break it down: so for example you can talk ratios of debt-to-GDP, you can talk ratios of government spending.

"The fundamental point we're trying to make is there's a tremendous amount of wasteful spending here. Actually it's about where it's being deployed to, you don't borrow money just to run your day-to-day expenses," Luxon said.

Luxon gave some cautious backing to Reserve Bank Governor Adrian Orr after Bridges was sharply critical of him in a recent podcast.

Bridges told The Working Group podcast that he did not want to see Orr reappointed.

"I don't see anyone on the centre right wanting to do that," he said.

"This is a guy who ... ultimately ... has probably made things worse.

"His policy implementation has led to the housing problems; we've got the big inflation, and he's been focused on a whole bunch of other things that may or may not be important."

But Luxon distanced himself from this position on Tuesday.

"That's not our position," Luxon said.

Luxon earlier confirmed he had spoken to Bridges about the remarks.

"What Simon was raising was fundamentally there has been mission creep with the Reserve Bank. We don't want it to get politicised because we don't want to undermine the independence and the trust that it has both with the Government and the public."

National's caucus meeting also saw the election of Chris Penk as Senior Whip and Maureen Pugh as Junior Whip.

"Chris and Maureen bring the integrity, experience and commitment to make a fantastic Whips team, and I look forward to seeing them flourish in their new roles," Luxon said.