UPDATED 10.21am: Jacinda Ardern has been cemented in the deputy leadership role with unanimous backing from the Labour caucus.

Labour's caucus met this morning to vote on the role of deputy after Annette King decided to step down from the role.

That decision came after Ardern won the Mt Albert byelection, after which Andrew Little and King both endorsed her for the role of deputy.

Ardern said she was grateful for the support from caucus and was "buoyed by the support the team has shown me for this role."

She had spoken to each MP before the vote was held.

She said Labour had more to offer for the younger generation.

"[National] has basically said anyone born from 1972 will be paying the cost for Bill English not putting in contributions to the Super Fund."

"He's effectively said that it's my generation that now has to pick up the tab."

She said that was the same generation that had to pay for their own tertiary education through student loans.

This change, alongside the re-entry to Parliament of List MP Raymond Huo, means Andrew Little will also make a minor portfolio re-shuffle.

The new Mt Albert MP is not expressing any preferences for what she'd like, or even if she wants to pick up responsibility for health, which is being vacated by Annette King.

"That's all for Andrew to determine but certainly I've made it clear that the portfolios I have are ones I feel passionate about."