National MP Simon Bridges has been given the key finance and infrastructure portfolios by new leader Christopher Luxon - handing him the third ranking in his caucus. 

Luxon is making the announcement in Tauranga today - the first major move of his leadership ahead of a wider re-shuffle next Monday. He pointed to Bridges' background as a transport minister as being important in the new role. 

He said his "good friend" Bridges could not make it to the event, because his son had had an accident at school, and Bridges was with him at hospital. 

Luxon said Bridges had the skills and "intellectual heft" needed for the finance portfolio. 

He had a "good brain and a great work ethic". 

"Simon Bridges taking it to Grant Robertson is going to be a great contest." 

"Simon is the guy we need to go up against this government." 

Asked if he trusted Bridges, Luxon said he had asked all his colleagues if they wanted to put the past behind them and it was about making sure the right person was in the right job. 

"Absolutely I totally trust him," he said. 

They had been friends for a long time. He had come to Tauranga because he wanted to come to see Bridges here, and the greengrocer - a family run business - where the standup is being held. 

"Simon will play a central and critical role in our leadership team, and he and I will work closely together." 

"He is ideally suited to prosecute the wasteful spending decisions, spiralling debt and rising costs of living occurring under the Labour Government. 

"The conversation after the last four years has been very honest." 

On rebuilding National's credibility, he said it was about starting to deliver. 

"I come with no baggage from recent events, caucus have wanted me to do that job, pull them together and unify them." 

He said to the 413,000 voters National had lost "we want you back." 

Luxon was elected unopposed as National's leader on Tuesday. Nicola Willis was elected as his deputy. 

Bridges pulled out of the race an hour before the National caucus were due to vote, and announced he would support Luxon, but has not spoken publicly since. 

While he did not have enough support to win the leadership, he does have a significant base of support in caucus. 

Luxon said the economy would be a priority for National and it intended to hold Labour to account over its spending decisions and the rising cost of living. 

He said spending on hospitals and roads was important but "blowing cash on nice-to-haves is quite another thing." 

"High inflation is like a thief in your pocket, making it harder to live. That's why public spending must be brought under control – otherwise we will keep seeing costs rising faster than wages." 

He said it was important the economy was sustainable, and that mean spending effectively and with discipline. 

"New Zealand needs a strong economy so we can invest in better core services like healthcare, education and police." 

Luxon said it was also important to reset the approach to infrastructure to take a long-term, intergenerational view. 

Parliament is in recess this week, but will return next Tuesday when Luxon will go head to head against Prime Minister Jacinda Ardern for the first time. 

Since he took over as leader, Luxon has said there would be jobs for all three former leaders in his caucus - Collins, Bridges and Todd Muller - saying "we'll set the baggage aside." 

It remains unknown whether Muller now wants to reverse his decision to retire in 2023 - a decision forced on him by Collins after she found out he had anonymously badmouthed fellow MP Harete Hipango to media. 

Luxon was elected leader after a dramatic four days in which Judith Collins was removed in a vote of no confidence by caucus last Thursday. 

That was prompted by her attempt to demote Bridges over comments he had made to MP Jacqui Dean at a caucus function in 2016, which Dean had mentioned to Collins in recent weeks. 

Bridges - who had apologised to Dean soon after the incident - had claimed it was a desperate bid by Collins to hold onto her leadership as speculation mounted he planned to roll her. 

Shane Reti stood in as interim leader for the four days until the caucus met to elect a new leader - and Bridges withdrew after realising he did not have enough support.