Josephine Cashman sacked from Indigenous advisory body after letter published by Andrew Bolt

The Aboriginal businesswoman Josephine Cashman has been sacked from her government advisory role, after allegations that she provided a faked letter from a senior Aboriginal leader as part of a campaign to discredit the author Bruce Pascoe.

In a brief statement the Minister for Indigenous Affairs, Ken Wyatt, said Cashman’s actions were “not conducive to the constructive and collaborative approach” needed on the advisory council on an Indigenous voice to parliament.

Wyatt said he had consulted the advisory group co-chairs, Prof Marcia Langton and Prof Tom Calma, and decided Cashman’s membership of the group was no longer tenable.

Related: Ken Wyatt may ask for resignations from Indigenous body after Bruce Pascoe controversy

NITV revealed on Tuesday that a letter denouncing Pascoe, supposedly written by Warramiri elder Terry Yumbulul, and published by the News Corp columnist Andrew Bolt by Cashman, was not Yumbulul’s work.

“I wish to make clear that the letter published in my name on Andrew Bolt’s blog … was not written by me,” Yumbulul said in a signed statement provided to NITV editor and Guardian columnist Jack Latimore.

“The statements attributed to me in that article ... are incorrect.

“The words attributed to me criticising other Aboriginal leaders are also false. I made no such remarks,” the statement, signed by Yumbulul and supplied to NITV news, said.

“The Warramiri people would never pass judgement on whether someone is Aboriginal or not. It is not our place to say.”

It was also revealed that large sections of the letter published by Bolt were almost identical with parts of an academic paper published in 1995 and freely available online.

Bolt had called for Wyatt’s resignation for “threatening a whistleblower” – Cashman.

The letter surfaced after Wyatt told Guardian Australia “the Pascoe debate is led by one of our own, which is a pity because it’s been played out publicly”.

“It’s something that we should deal with within the community.”

Wyatt said he would not rule out asking for resignations if the issue “becomes detrimental to the work of the voice”.

“I have to think of the greater good of Aboriginal and Torres Strait Islander people as opposed to a debate between two significant individuals,” he said at the time.

Professor Marcia Langton, co-chair of the senior advisory group, told the Guardian: “I welcome the minister’s decision on this matter.

“Ms Cashman created too many distractions to the very important work of the senior advisory group on the voice co-design. We have important work to do and we need members of the senior advisory group to deliver well-considered advice to the minister.”

Cashman had also asked the home affairs minister, Peter Dutton, to investigate Pascoe for allegedly benefiting financially from claiming to be Indigenous. Dutton referred the allegation to the Australian federal police, who found that “no commonwealth offence had been committed”.

Wyatt said he found it “fascinating” that identity seemed to be broadly accepted with every other group, while Indigenous Australians were questioned.

Wyatt said it was vital that young Indigenous people saw strong leaders “who are measured in their responses and who provide examples of how you can deal with challenges and work to a solution in a way in which we’re not fighting each other publicly on social media”.

Bolt claimed the letter came to him from Cashman, and has published extracts form emails which he said showed Yumbulul was involved in drafting the letter. But he has “asked Terry [Yumbulul] to explain his apparent change of mind”.

Bolt also claims the Indigenous leader was copied in on a final email which authorised the publication of the column on Australia Day. But he did not comment on claims that the letter plagiarised an academic paper and website.

A spokesman for News Corp Australia declined to comment.