In short:

A man who volunteered for One Nation during a West Australian by-election was previously named in a federal tribunal ruling as someone who promoted neo-Nazi ideologies.

David Donis handed out how-to-vote cards and attended the party's victory event, sparking questions about One Nation's vetting processes.

What's next?

WA's One Nation leader Rod Caddies appears to have pre-empted the revelation, saying if an extremist had infiltrated the party, they would be expelled.

A man who volunteered for One Nation during the party's successful West Australian by-election was previously named by a federal tribunal for promoting neo-Nazi ideologies.

David Donis handed out how-to-vote cards for One Nation in the state seat of Secret Harbour last month, sparking fresh questions about vetting months after Pauline Hanson revealed the party had shut branches she said were "infiltrated by extremists".

Mr Donis was a founding member and president of the Society of Western Australian Nationalists (SWAN), a now-deregistered organisation the Administrative Appeals Tribunal (AAT) found was a racist extremist group.

The tribunal's comments about Mr Donis were made in a 2023 case concerning an army reservist's security clearance.

Mr Donis was identified by other political volunteers at the Singleton Primary School polling booth on August 27 and later pictured standing near the stage at One Nation's victory party that night.

Two people told the ABC there was an incident during the day where Mr Donis yelled at a voter leaving the polling station, prompting other volunteers to intervene and calm the situation.

A One Nation spokesperson said the individual identified by the ABC as David Donis was "not a member of One Nation".

"Our party does not condone extremist views, and where such issues are identified they're acted upon swiftly by the party," the spokesperson said.

It is understood Mr Donis was a volunteer rather than a formal member and would not be permitted to continue associating with One Nation.

A Liberal source told the ABC that Mr Donis had previously been a member of their party as a teen but ultimately left when it was made known his views were "not welcome".

Mr Donis has previously denied promoting neo-Nazi ideologies, but in 2023 the AAT said it was satisfied he and other SWAN members had done so.

One Nation's vetting has previously come under scrutiny, with Senator Hanson revealing in June that the party had shut down four branches.

"I'm being infiltrated by these extremists, so it's all the time happening with One Nation; they set us up all the time," she told Nine papers.

One senior West Australian Liberal told the ABC that One Nation has had "years of warnings" about problems with candidates and people associated with the party.

They said background checks should be "second nature".

"That includes basic vetting to ensure people publicly representing the party do not have verifiable links to neo-Nazis, white supremacists or organisations advocating political violence," the Liberal said.

Man adhered to "neo-Nazi ideologies"

In mid-2023, the AAT accepted evidence Mr Donis was a member of SWAN, which it determined was a "nationalist and racist extremist group".

Mr Donis denied the allegation, but the tribunal said it was satisfied he and other SWAN members "adhere to, and promote, racist and neo-Nazi ideologies" and supported politically motivated and communal violence.

The findings about Mr Donis emerged in a case in which the AAT upheld ASIO's decision that an army reservist posed a security risk and should lose his NV1 clearance.

The AAT said the reservist had close ties to Mr Donis and SWAN, which the tribunal accepted was a nationalist and racist extremist group after hearing "closed evidence" — classified material that could not be disclosed publicly.

The case noted SWAN had come into existence in about 2018 or early 2019, with Mr Donis as a "founding member and president".

Incorporation documents show SWAN members voted to voluntarily deregister the organisation due to "inactivity" in October of 2023, three months after the AAT findings.

One Nation WA pre-empts volunteer revelation

West Australian One Nation leader Rod Caddies appeared to pre-empt the potential controversy surrounding a party volunteer last week in a video shared to social media.

Mr Caddies criticised state Liberal MP Anthony Spagnolo for submitting a series of questions on notice to the Labor government "probing some tie" between One Nation's "Secret Harbour campaign and neo-Nazis".

He accused Mr Spagnolo of taking a page out of the "radical left playbook" by "trying to take One Nation down and tie us to Nazis".

"I don't know what sad little 'gotcha' the member thinks he has. I suspect it's something about some low level volunteer or some link like that,"the WA One Nation leader said.

Mr Caddies said if that were the case it meant the Liberal Party would have to own "everything their volunteers have said or done".

"The next time someone loosely affiliated with the Liberal Party has a shady background or says something crazy, I'll make sure every one of their members are set to the same standard you set," he said.

Mr Caddies then said even if the Liberals did "uncover something" it would not prove anything.

"If it turns out some idiot has managed to weasel his way into One Nation, we'll expel him; that's simple. If an extremist has infiltrated One Nation, it's by hiding their extremism," he said.

Volunteer witnessed shouting at voter

Mr Donis initially attracted the attention of volunteers from other political parties at a Secret Harbour by-election polling booth last month after he yelled at a voter.

One witness said it was before midday when they saw Mr Donis interact with a mother and daughter leaving the venue after voting.

They overheard Mr Donis wish the pair a "good day" before adding he hoped they had put One Nation "first" and Labor "last" on the ballot paper.

The witness said the woman replied she was more likely to put One Nation last, which prompted Mr Donis to accuse her of supporting abortion and setting a "bad example" for her daughter.

They said the woman gave a dismissive response, but Mr Donis continued to yell as she walked away across the car park.

The witness said the One Nation "booth captain" at the school intervened to try and quiet Mr Donis, as did a nearby Liberal member who urged him to "settle down".

They said there were no further incidents at the booth involving Mr Donis that day.

Later in the evening, Mr Donis was spotted at an event for supporters of One Nation candidate Luke Herdegen.

The ABC has been unable to contact David Donis.