ACT's David Seymour says his party has "done a very good job" with vetting potential candidates, but acknowledges "some that have slipped through the net".
It comes after a candidate resigned over a comment they posted likening the vaccine mandate rollout to Nazi concentration camps.
Elaine Naidu Franz was the party's Rangitata candidate and 29th on the party list.
In response to a LinkedIn post by Seymour around a year ago, 1News reports Franz said: "If you are wondering how the Nazis were able to come into power and do all the horrific things that they did, well you are looking at the start of the process right here. So Mr Seymour, when can we expect those who are unvaccinated to start wearing armbands? When can we expect to see concentration camps and re-education camps? When can we start expecting to see troops on our streets rounding up people?"
In another post, she said Seymour needed to "have the balls to front up to the people outside [Parliament]".
Seymour told media on Wednesday her comments were "unacceptable" and she has since resigned.
"That's absolutely unacceptable as I've said and that person will no longer be a candidate for the Act Party."
It comes as a second candidate, Darren Gilchrist, apologised for social media comments incorrectly linking drowning to the COVID-19 vaccine.
According to 1News, 18 months ago Gilchrist posted on Telegram: "Well over 40 drownings this summer so far. Given the jab side effects of myocarditis/heart attacks, and blood clotting, I'm thinking there is a likely link to jabs."
In another post Gilchrist, who is ACT's candidate for Waikato, referred to former Prime Minister Dame Jacinda Ardern as "Jabcinda".
Seymour said Gilchrist has since apologised for his comments and no longer agrees with them.
Gilchrist confirmed to 1News that he no longer agrees with his previous comments.
He said he was "just asking questions" and wasn't his "genuine belief". He said the comment about Dame Jacinda was inappropriate and he has "no objection to people deciding to get vaccinated or not".
"I was very upset at mandates, which I think a number of New Zealanders were," he told the outlet.
Seymour pushed back on suggestions his party was attracting extreme views on Wednesday. The ACT leader told reporters his party vets candidates well and he "regrets" some have slipped through the cracks.
He said candidates were interviewed by the party's board, had their social channels trawled through and reference checked among other things.
"We have done quite a number of things," he said. "We have actually done a very good job of vetting over 60 candidates. There are some that have slipped through the net and they are now gone."
He went on to say he is "pretty pleased" with the party's vetting process.
"I deeply regret that this person has slipped through the net. I find the comments unacceptable but we dealt with it in literally 15 minutes, they are no longer a candidate for us."
When asked whether he was confident there was no one else on the list who might need to go, he said "You never say never".
"I think we've made a very good effort at vetting our candidates. We strongly regret that one person, in particular, slipped through that net. They're no longer a candidate and obviously, we keep our eyes open."
