The caucus met at Parliament this morning to decide who would slot into the number two spot after Gerry Brownlee announced he would step aside late last week.
Heading into the meeting, Brownlee endorsed Dr Reti - who is National's health spokesperson - to take over the role.
"The issues the country is going to face over the next couple of years are going to be much more determined by the Covid-19 response," he said.
"Shane Reti will provide good support for Judith given that particular focus."
RNZ understood Reti was also Collins' favoured option though she is publicly refusing to reveal her preference.
"My preferred option will be whoever caucus delivers," Collins said.
Both Collins and Reti, who were selected unopposed, were confirmed as leader and deputy leader this afternoon
“It is an enormous privilege to be reconfirmed as Leader of the National Party,” Ms Collins said.
“I’m looking forward to leading a strong, united and focused Opposition that will deliver for all New Zealanders.
“I’m delighted by Dr Shane Reti’s appointment. He is a hard-working, intelligent MP with all the skills needed to be an effective leader. His detailed examination and prosecution of the Government’s handling of Covid-19 helped improve the response for New Zealanders.
“Dr Reti’s knowledge and history working in the health sector will be an asset as Parliament deals with the impact of Covid-19. His experience will be invaluable to me as deputy leader and I’m looking forward to working closer with him.”
The National Party Caucus also voted on two Whips, with Matt Doocey selected as Senior Whip and Maureen Pugh selected as Junior Whip.
Per the party's rules, Collins faced a confidence vote, but ahead of the caucus meeting she told reporters she expected to retain the leadership.
Rotorua MP Todd McClay and list MP Michael Woodhouse had been touted as potential contenders for the deputy position, but both ruled out making a tilt.
"I won't be offering myself in that role," Woodhouse said. "I wish the person who does get that role every success."
McClay told reporters Reti was the "best person" for the job.
"He resonates with New Zealanders, he has a very good command of some important policy areas, and he has the respect of caucus."
Former leadership aspirant Mark Mitchell also ruled out a run for the deputy position.
He said he would wait to see who was nominated, but saw merit in having a "genuine medical doctor" in the leadership team during a pandemic.
Waimakariri MP Doocey declined to say who he would support, but described Reti as a "top guy" whom the caucus was lucky to have.
Collins had earlier signalled she would unveil her new line-up and their responsibilities after the leadership team was confirmed.
She was coy when questioned about the reshuffle, but told reporters to expect "surprises".
"Anything that happens in the caucus stays in the caucus," Collins said.
It is widely expected that list MP Paul Goldsmith will lose the finance portfolio following a series of errors in the party's alternative budget.
"We were fighting hard to win an election," Goldsmith said.
"We had a very bad result, I had a senior role, and I'm fully accountable."
