A week after Jacinda Ardern shocked the nation with her announcement she would be resigning her post as Prime Minister, her former deputy Grant Robertson has said he is pleased he did not have to put his name forward.

Robertson was initially tipped by many as an obvious replacement for Ardern, having contested the leadership twice previously and serving as her deputy and Finance Minister.

"I have been up close to the job of prime minister over the last five years and I know it's a step up," he told Tim Dower on Newstalk ZB.

"Actually, I reckon it would have been a bit dishonest of me if I'd gone for it because it's a job you have to have one hundred percent desire to do," Robertson said.

Chris Hipkins eventually took on the role without opposition, and Robertson said his job was now to support his new leader.

"The good news is, I didn't have to put myself forward for a job that I didn't have that one hundred percent desire for, because we have Chris Hipkins who wants it and who is going to be very good at it and I'm here to support him."

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