She might be one of the most popular Prime Ministers of all time, but that hasn't stopped Lisa Wilkinson from asking Jacinda Ardern the difficult questions.

On the Sunday Project, Lisa wasted no time grilling the PM, declaring she'll "probably get criticised" for doing so.

After discussing how New Zealand is doing four months after the terrorism attack in Christchurch, Lisa tackled Ardern's recent criticism of Australia's policy to deport New Zealand criminals, news.com.au reports.

The usually poised Ardern appears to squirm awkwardly and looks visibly uncomfortable as Lisa boldly quizzes her in front of the camera.

"You've described Scott Morrison's stance on deportations as 'corrosive', Lisa states.

Ardern begins: "Oh look I think we should be fair the, the deportation policy has existed for a while and …"

Perhaps sensing her hesitation, Lisa helpfully chips in, branding ScoMo "the architect" of the policy Ardern described as "wrong" and "unjust" on Friday, following a meeting with the Australian PM.

"That is, that is correct," Ardern says. "When you are friends as we are, you can speak frankly with each other you know."

"I think it speaks to the strength of it that we do speak so openly," Ardern adds.

The interview was filmed shortly after the meeting with ScoMo, in which the leaders discussed "frankly" the implications NZ citizens living in Australia have faced since it tightened back in 2014.

After the pair's face-to-face — their first since the Coalition won the May election — Ardern said New Zealand wasn't going to let go its concerns after more than 1,500 Kiwi criminals have been deported since the rules changed.

"If something's wrong and if something is not fair and is unjust, you don't let it go," she told NZ media after the meeting with Mr Morrison, the ABC reported.

"I totally accept that it is within Australia's rights to deport those who engage in criminal activity in Australia. But there are some examples that will not make any sense to any fair-minded person."

Later in the interview, Lisa probes Ardern on motherhood, anticipating her line of questioning may not prove popular with some viewers.

"Now I'm probably gonna get criticised for asking you this, you are a strong, successful, working women but I think people are genuinely interested. How are you going with motherhood?" she said.

After awkwardly squirming her way through her stance on Australia's "corrosive" deportation laws, it Ardern seems happy to move onto a lighter topic.

Declaring she "doesn't mind" talking about what life has been like since becoming a mum to daughter Neve with fiance Clarke Gayford, she goes on to shower him with praise for being the one-year-old's "primary caregiver".

"No one needs to see anyone pretending it's easy because its not and so I'm not going to go around pretending I do everything," she said, shrugging off claims she "this Wonder Woman". "I'm not, its hard and women who are both working and raising children deserve to have help and support and so we shouldn't pretend it can be done alone."

As Lisa predicted, some viewers were quick to question her decision to ask Ardern about her life as a mum.

Ardern also went on reveal some details about her daughter, stating she's "very strong willed" — saying the personality trait was a mix of both her mum and dad.

In a post on her Instagram account before the show aired, Lisa revealed Ardern had "never told anyone" those details about Neve before.

Ardern also opened up about her recent engagement to Clarke, joking she had no idea it was coming.

"If I did, I wouldn't have been wearing sweats," she laughed.

The pair got engaged over Easter during a hike, with Ardern revealing Clarke presented her a diamond ring inside an Easter egg.

Viewers have been loving the interview, taking to Twitter to praise Ardern for being "normal".