The firebrand Victorian Greens senator received confidential briefings about organised crime whilst in a relationship with a former organised crime gang president, it has now emerged.
Now former Greens deputy Senate leader Lidia Thorpe has resigned as the party's deputy in the Senate for failing to disclose a relationship with a former bikie boss.
The ABC revealed Senator Thorpe had not disclosed she was in a relationship with former Rebels president Dean Martin while serving on the parliamentary law enforcement committee.
The committee had been receiving confidential briefings about bikie gangs at the time.
Greens leader Adam Bandt requested Senator Thorpe's resignation from the party leadership in the wake of the revelations, which she accepted.
He said her Victorian colleague's failure to disclose the relationship was a "significant lack of judgment", telling reporters on Thursday:
"As leader I expect my senators and MPs, especially those in leadership positions, to exercise good judgment.
"At a minimum, Senator Thorpe needed to disclose to me her connection to Mr Martin and her failure to do so showed a significant lack of judgment."
Senator Thorpe conceded in a statement that she made a mistake:
"I ... have not exercised good judgment.
"I will now reflect on this and focus on my important portfolio work, especially advocating for First Nations people."
Prime Minister Anthony Albanese said on Thursday the revelations about Senator Thorpe's relationship were concerning.
"Australians are entitled to believe that the oversight processes over the legal system will be maintained in a way that ensures integrity and ensures that any information which is given there is kept in a confidential basis," he said.
"I note that Senator Thorpe has said that this is an error of judgment - that is the least description that I would put to it."
Labor's Jason Clare said that looked like a clear conflict of interest, telling national television on Friday:
"You can't be on an inquiry investigating outlaw motorcycle gangs and be in a relationship with an (ex) outlaw motorcycle gang member, a bikie."
"It seems to me just to be a no-brainer here that there is a massive conflict of interest."
Liberal deputy leader Sussan Ley said there were serious questions to answer, and challenged Labor to back a censure motion against Senator Thorpe when federal parliament sits next week.
"You can't be receiving confidential briefings during the day about outlaw motorcycle gangs and be in bed with one of them at night. That's not on," she told Sunrise.
"As I understand it, there will be a censure motion moved in the Senate ... I hope [Labor] support it."
Country Liberal NT senator Jacinta Nampikinpa price posted on Facebook on Thursady night that Thorpe was benefitting from a double-standard compared to how right-of-centre politicians would be treated in the same circumstances:
"Correct me if I’m wrong but if a conservative politician had a public list of down right disrespectful, unbecoming, unstatesmanlike and career ending transgressions as long as this they’d be stripped of their position completely!
The senator accused Senator Thorpe of regularly attacking colleagues on the basis of their skin colour, supporting protestors who set fire to Australia’s first Parliament House and supporting the burning of the Australian flag.
Mr Bandt said he was not aware of the revelations about Senator Thorpe's relationship until he was contacted by the media. He said it was disappointing the relationship was not disclosed:
"People are entitled to trust that where there are issues that affect the work of senators, all members of parliament, that they will be disclosed.
"It is disappointing because it is an error, a significant error of judgment from someone who has a lot to offer this country and a lot to offer this parliament."
Mr Bandt said the senator had not been involved in the justice portfolio since the May federal election.