The federal Greens leader, Richard Di Natale, has called for NSW MP Jeremy Buckingham to stand aside over allegations of inappropriate behaviour towards women, as the state branch descended into an angry split over the upper house member’s future.

Earlier on Tuesday, Greens senator Mehreen Faruqi and NSW MP Jenny Leong publicly called for Buckingham not to contest the next election. But Buckingham’s fellow MLC Cate Faehrmann defended him, saying, “As a woman, I am angry at the way this complaint has been used as a political weapon.”

Leong said under privilege in the NSW lower house: “Jeremy’s actions and behaviour – some widely reported and documented and some still held in confidence, which must be respected – have had a real and lasting consequence on individual women, members and formal members of our party as well as active volunteers in our party ... I know there have been active volunteers who have stepped aside or resigned as members as a result of Jeremy’s behaviour.”

In the wake of Leong’s speech, Di Natale issued a statement saying he believed it was best for Buckingham to stand aside “as a candidate for the next election”.

“This is ultimately a matter for the Greens NSW, but in light of the serious issues raised in NSW MP Jenny Leong’s statement today, I believe the most appropriate course of action is for Jeremy Buckingham to stand aside as a candidate for the next election,” Di Natale said.

“I have communicated that to Jeremy today on behalf of the federal party room.”

Buckingham, a member of the state upper house, faced an independent investigation earlier this year over allegations he behaved inappropriately toward a Greens aide in 2011. Buckingham said the investigation – conducted by independent firm Workdynamic Australia – cleared him of any wrongdoing.

The full report has not been released, though Buckingham has released advice he received about its “final recommendations”.

Leong did not detail any new allegations about other women in her speech to parliament. But she accused Buckingham of acting in an “aggressive and intimidating manner” towards her.

“On two occasions earlier this year Jeremy behaved in an aggressive and intimidating manner towards me, once in a public place and once in the corridors of this place,” she said in the speech to the NSW lower house.

‘“I have spent many days in this bear pit, and I know that politics can be an intense place. But as too many women know, you can feel the difference, you can feel the difference between when a man is in control, and when he is not.”

Buckingham earlier issued a statement denying Leong’s allegations. He also said the accusations of misconduct against him had already been investigated with no finding of wrongdoing.

“I reject Jenny Leong’s characterisation of a couple of conversations we’ve had,” Buckingham said.

“I’ve been democratically elected to the parliament and to the NSW Greens Legislative Council ticket by a ballot of all members.”

Faehrmann defended Buckingham, saying the original allegations had been investigated and found unsubstantiated.

The NSW MP Jenny Leong set off a huge row in the Greens on Tuesday by using parliamentary privilege to accuse her party colleague Jeremy Buckingham of inappropriate behaviour. Photograph: Dean Lewins/AAP

Faehrmann, previously Di Natale’s chief of staff, said Buckingham had been targeted by a “determined group of people in the party” who had “relentlessly pursued” him to resign.

“As a woman, I am angry at the way this complaint has been used as a political weapon,” Faehrmann said. “This risks making it harder for all women who have experienced sexual harassment and assault to feel safe and supported to come forward.”

“Women’s complaints should always be taken seriously, believed prima facie and investigated professionally and independently. However, this does not mean we are all then at liberty to act contrary to the findings of the subsequent investigation.”

In her speech to parliament, Leong apologised for failing to speak out earlier, saying this was the first opportunity she could use parliamentary privilege, something she said showed the need for defamation reform.

“Jeremy, you have had countless opportunities to take responsibility for this, to apologise to those impacted, and to seek to address them. Instead you have followed with further aggressive tactics,” she said.

“I know you feel like you are the victim of internal party attacks, but you must acknowledge your role in this and stand aside before more damage can be done.”

She said the Greens would be unable to deal with its internal problems until Buckingham stepped aside.

“Jeremy Buckingham must step aside because we won’t be able to resolve these or other issues in our party or to address the problematic behaviours or rebuild trust while the perpetrator of serious harms continues to remain in our party,” she said.

“While I might be fearful of the reactions and repercussions of doing what I’m doing now, it is nothing … compared to the feeling felt by survivors.”

Last week, allegations against former NSW Labor leader Luke Foley caused an internal crisis for the state opposition and led to Foley’s resignation and replacement as leader by Michael Daley.

The joint statement from Faruqi and Long said: “This is in the best interests of the complainant, members, supporters and volunteers,” the joint statement said. “We are both very proud of our collective progressive movement – the Greens and its wonderful members and supporters. But at the moment, both this project and the people who are part of it are suffering.”

The findings of the Greens investigation have not been released. In September, the party said in a statement that the investigation could not find sufficient evidence to prove misconduct by Buckingham.

“Although the factual context of a social gathering on 26 August 2011 did take place, Workdynamic was ‘not satisfied that there is sufficient evidence on the balance of probabilities that an incident of sexual harassment as defined by the legislation occurred’,” the Greens said.

Buckingham has previously denied the allegations and said they were used to try to “destroy” him, saying they had been difficult and damaging. He said he was pursuing civil action against the ABC for a story detailing the allegations.

The Greens’ general handling of sexual harassment complaints has prompted the federal leader, Richard Di Natale, to apologise to several women.