Lidia Thorpe resigns as Greens deputy leader in Senate over relationship with former bikie boss

Senator Lidia Thorpe has resigned as deputy leader of the Greens in the Senate over what leader Adam Bandt called a “significant lack of judgment” for failing to declare a relationship with the former president of the Rebels bikie gang.

On Thursday the ABC revealed Thorpe had confirmed she “briefly dated” Dean Martin in 2021 and remains friends with him. In a statement, Thorpe accepted she had “made mistakes and … not exercised good judgment” over a failure to declare the relationship.

The relationship reportedly sparked staff concerns about a possible perceived conflict of interest with her duties on the joint parliamentary law enforcement committee.

Guardian Australia does not suggest that Thorpe shared any confidential information with any person not authorised to receive it.

Martin, who has no criminal convictions, was associated with the Rebels but stepped down as Victorian chapter president in 2018 after his brother Shane Martin – the father of AFL star Dustin Martin – was deported to New Zealand.

On Thursday Bandt told reporters in Melbourne that he “wasn’t aware” of the relationship until it was raised by the media.

Bandt said that “at a minimum” Thorpe needed to declare her relationship with Martin and in failing to do so she showed “a significant lack of judgment”.

“Thorpe says she now understands this … Thorpe has told me at no stage was there any breach of the rules of those committees and their work, and no sharing of confidential information.”

“But that’s not enough. It was clear this could be perceived as affecting her work and her failure to disclose that to me was an error of judgment.”

Bandt noted that Thorpe had not held the justice portfolio since the election, but said she still had “important work to do on First Nations justice including on progressing Truth, Treaty and Voice”.

Bandt said he had contacted the Australian Federal Police to “see if they have any concerns with respect to disclosure of information” but “at the moment … no one is suggesting that that happened”.

Bandt said that resignation “on the facts that I [have] at the moment, is an appropriate sanction”, adding “of course I will consider further action if those facts change”.

In a statement, Thorpe said Bandt had “requested my resignation as deputy leader in the Senate and I have given him [it]”.

“I accept that I have made mistakes and have not exercised good judgment.

“I will now reflect on this and focus on my important portfolio work, especially advocating for First Nations people.”

In a statement to the ABC, Thorpe said she met Martin “through Blak activism and briefly dated in early 2021”.

“We remain friends and have collaborated on our shared interests advocating for the rights of First Nations peoples.”

Related: Lidia Thorpe wants action on treaty and truth before campaigning for Indigenous voice

Thorpe acknowledged she did not advise Bandt of her relationship with Martin, but insisted that confidential committee documents on how the AFP monitors outlaw motorcycle gangs were “treated in confidence”.

Thorpe said Martin’s history with the Rebels was a “past connection”. “Obviously, I’m concerned about the criminal activities of outlaw motorcycle clubs in general. But when we met, Mr Martin was no longer involved with that world.”

According to the ABC, one staffer raised their concerns with Bandt’s chief of staff, Damien Lawson. Lawson denied through a spokesperson that he told the staffer not to raise the issue with Bandt, but said he counselled them to raise it anew with Thorpe.

“Mr Lawson subsequently understood that this had happened and the concerns had been addressed,” the spokesperson reportedly said.

Bandt said that Lawson was a “good and competent chief of staff who makes many good decisions” but added “this was not one of them”.

“I should have been told about this, and I have made that clear to my chief of staff, and I have counselled him.”

Prime minister, Anthony Albanese, told reporters in Albany, the revelations were “concerning” and that an error of judgment is “the least description I would put to it”.

Albanese called on Bandt to explain what his office knew about the issue, and to explain why he had not been informed personally.