A Greens candidate has apologised for social media comments in which he said he wanted to "f---ing kill politicians", while his party leader acknowledged issues with candidate vetting.
James Cruz apologised for the comments and said the suggestion of violence was inappropriate.
"I wrote one of those posts nine years ago and the other over 10 years ago. I regret using those words and I would not use them again," Mr Cruz said in a statement.
"I want to reiterate that I disavow all violence and I support wholeheartedly the Greens' core values of peace and non-violence."
Greens leader Shane Rattenbury said social media posts had "slipped through the cracks" in the party's vetting process.
"These posts are nearly a decade old and clearly in the process of checking, they've been missed. That is regrettable," Mr Rattenbury said.
He welcomed Mr Cruz's statement and expression of regret about the comments.
"The commitment to peace and non-violence is just in the DNA of the Greens. It's one of our founding principles. ... Of course, people sometimes, in the heat of the moment, will make regrettable comments," Mr Rattenbury said.
"And I think it's upon leaders to think carefully about their language and think about how we reflect community sentiment, but also how we shape community sentiment."
Chief Minister Andrew Barr had earlier decried the "hateful and risky statements" that had been made by Mr Cruz.
"All it will take is one person to misinterpret them and we could have a tragedy on our hands. We are seeing in other Australian cities, some quite significant political violence occurring. We don't want that in Canberra," Mr Barr said.
He said Mr Cruz's comments had no place in the ACT's democratic process, but played down any suggestion of concern about Labor re-entering a governing agreement with the Greens.
"What we are seeing, I think, is a difference between [the Greens'] more experienced, if you like, professional politicians and some of their support candidates," Mr Barr said.
Mr Cruz, who is running in Kurrajong, has been placed last on the Greens' how-to-vote card.
The Australian on Monday reported Mr Cruz had written on social media that he did not "give a shit" about Israeli forces dying "when they couldn't care less about indiscriminately slaughtering civilians and actively cheer as they die".
Opposition Leader Elizabeth Lee had said the Chief Minister needed to be upfront about whether he shared the "very dangerous views" of a candidate from a party with which Labor has governed.
Mr Rattenbury's response to the comments "should really ring some alarm bells for many Canberrans", Ms Lee said.
Ms Lee said she was unaware of advertisements placed on Facebook by Jason Wood, the Liberal member for La Trobe in the federal parliament, about ACT Greens candidates Harini Rangarajan and Mr Cruz, whom the advertisements dubbed "extreme".
Ms Lee said: "I've not seen the ads. I've never had any discussions with that federal member and I don't know anything about those ads."
Last week the Greens defended blog posts written by Harini Rangarajan, which compared Osama bin Laden with Jesus Christ.
The party said it was "creative writing" and did not reflect the 20-year-old's personal views, but Mr Rattenbury acknowledged the material could be concerning and confronting.
