Duncan Garner says Green MP Golriz Ghahraman "allowed herself to be painted as an angel" by not clarifying the work she did as a war crime defence lawyer in Rwanda.
Former Labour staffer Phil Quin, who has lived and worked in Rwanda, sent a series of tweets saying Ms Ghahraman should resign, claiming she is a genocide denier.
"I don't have any kind of problem with defence lawyers," Garner said on The AM Show.
"Everybody's allowed a defence lawyer, there's no problem with that.
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"The problem here is that she allowed this narrative to take place and to take hold that she was on the side of the good all the time when she was actually defending evil."
Ms Ghahraman did a three-month internship on the defence team for the trial of Joseph Nzirorera in Rwanda, who died before he could be convicted of genocide. She said she also worked on the appeals case for Simon Bikindi, who was convicted of using songs to incite the 1994 genocide.
Garner says Ms Ghahraman failed to clarify the work she did both in her profile on the Green Party website and in her maiden speech in parliament.
"She talks about the one case she prosecuted, [but] nowhere in her own words does she talk about defending evil.
"Quite frankly I didn't know this until this scandal broke.
"It didn't make the Green party website, it didn't make the speech she wrote herself. I'm sorry, not good enough."
Co-host Amanda Gilles says she too "assumed [Mr Ghahraman] was on the side of the prosecution".
"Everyone's entitled to a defence, we're not arguing that.
"But in politics perception is everything and she was perceived as a human rights battler.
"On the flip side, a reporter for NZME interviewed her six weeks ago, it was before the election... apparently Golriz did talk about it. She wasn't hiding it. It just didn't make the story."
Ms Ghahraman has talked openly about her defence work with VICE and in a NZME article published on Monday.
Ms Ghahraman told the AM Show she's been nothing but open.
"I did a number of interviews before the election where I talked about this. I went around various law schools, I've talked about this in the past. My CV was online and completely open.
"There's just this one line that people have gotten a hold of and I would suggest if the Green party was trying to hide this someone would have called me up and said you've got to stop doing Herald articles about it."
She says after discovering her profile on the Green Party website failed to explicitly mention her work as part of the defence teams, she says it was changed immediately.
"It's really hard to act on the defence in those trials but you've got to be really committed to that human rights-based process.
"You're there to make the process fair. So to say that there's a moral problem, to suggest that all of these United Nations lawyers, where the UN requires that there's a defence and a prosecution are somehow morally repugnant, is actually offensive to be honest.
"We want to know exactly who did what, we want it to be transparent we want the evidence to be tested and the historical record to be set right."