Mike Hosking, dressed in black T-shirt, asks Jacinda Ardern what she'll be wearing during leader's debate

Under-fire broadcaster Mike Hosking has asked Labour leader Jacinda Ardern what she'll be wearing during Thursday night's televised leader's debate.

Ms Ardern will face Prime Minister Bill English in the debate, hosted by Mr Hosking, despite more than 76,000 people signing a petition to have him removed as moderator.

The petition called the openly right-leaning Newstalk ZB and Seven Sharp host "consistently socially irresponsible", but he's promised Ms Ardern there will be "balance up the wazoo".

Ms Ardern was being interviewed on Newstalk ZB Thursday morning when Mr Hosking asked her how she was feeling ahead of the debate, Ms Ardern's first as Labour leader.

"I would be superhuman if I didn't have nerves. I think probably both of us would be nervous," she told him.

"What about outfit?" Mr Hosking, dressed in a black T-shirt and blue jeans, asked the 37-year-old.

"When you're thinking about colour schemes, you've got to think about the bloody backdrop behind you, don't you? I only actually started putting my mind to that properly yesterday, which is probably a bit last-minute," she replied.

"So you've got something sorted and you're ready to go?" he asked.

"I think so. I've got two options. I'm still thinking about it," she said. "Are you asking Bill that question too?"

"Of course I'll ask," said Mr Hosking.

"I want it framed in exactly the same way," insisted Ms Ardern.

"There will be balance up the wazoo," Mr Hosking assured her.

Broadcaster Mike Hosking shows off his characteristically casual style.
Broadcaster Mike Hosking shows off his characteristically casual style. Photo credit: Newstalk ZB

Ms Ardern has been Labour leader less than a month, and made international headlines when she returned fire at The AM Show co-host Mark Richardson after he said employers had a right to know if their female employees were considering getting pregnant.

Ms Ardern said while it was fair to ask her since she'd spent years ruling out a run for Prime Minister because she wanted to have children, it was "unacceptable" in most cases.

"It is totally unacceptable in 2017 to say that women should have to answer that question in the workplace. That is unacceptable in 2017," she told Richardson.

"It is the woman's decision about when they choose to have children. It should not predetermine whether or not they get the job."

The incident was memorialised on a T-shirt.

Another T-shirt made in the wake of her comments raised money for Women's Refuge

Jacinda Ardern on a T-shirt.
Jacinda Ardern on a T-shirt. Photo credit: Bold as Brass