The First Peoples' Assembly of Victoria has urged all people to seek information from trusted sources in the wake of revelations that false information in letters that featured the official Assembly letterhead were sent to landowners in North-West Victoria.

Assembly Member for the Wotjobaluk, Jaadwajali, Jadwaa, Wergaia, Jupagulk clans and Wotjobaluk man, Dylan Clarke, said he was horrified when learned of the news.

"It's terribly sad and extremely frustrating," said Mr Clarke.

"We're trying to have constructive conversations in the community, and someone is going to extraordinary lengths to poison the goodwill and scare people about all the positive things we can achieve together on the journey to Treaty.

The Assembly said that whilst the letter had an "upbeat tone," the underlying themes were designed to create fear around the acquisition of land.

The revelation of the letter comes in the wake of Victorian Nationals leader Peter Walsh using an opinion piece in the syndicated Australian Community Media publications to criticise the recent agreement between the Barengi Gadjin Land Council and the state of Victoria under the Traditional Owner Settlement Act.

Mr Walsh, who is also the Nationals Indigenous affairs spokesperson, used his column to slam the deal, calling it a "stealth attack" and an "attack on the rights of all Victorians." He said the state needed to reassess giving Aboriginal groups "sweeping powers to totally rewrite and run everything".

Mr Clarke, who also sits on the Barengi Gadjin Land Council, told the Age Walsh's comments "feel like a bunch of random complaints being lumped together."

Native title legal expert and former director of the Victorian Aboriginal Heritage Council Matthew Storey told the Age that Walsh was wrong, stating: "Either through ignorance or mischievousness, [Walsh] confuses matters dealt with in agreements under the Traditional Owner Settlement Act and cultural heritage management [under the] Aboriginal Heritage Act."

"Either way, it is fairly damning for a shadow Aboriginal affairs minister to get this wrong."

Mr Clarke said the letter was simply another version of the "coming after your backyard bullshit".

"Treaty is about finding better ways to work together and making sure Aboriginal knowledge and culture can be respected and shared and used to care for country and help our communities thrive," he said.

"But the lies in this letter are designed to depict us as something to be afraid of."

Assembly Co-Chair and Wamba Wamba, Yorta Yorta, Dhudhuroa and Dja Dja Wurrung woman, Ngarra Murray, said the letter had been referred to the police.

"This is what we are up against, outright lies and deception," she said.

"You have to think about why the people against the idea of Treaty or listening to First People feel the need to stoop to such low levels, it's shameful.

"These are illegal tactics designed to confuse people, when in reality Treaty is going to benefit everyone who calls Victoria home."

Ms Murray said the Assembly would help support Mr Clarke in working with and supporting the local community to write "genuine letters" to explain the facts and unfolding process of Treaty.

She encouraged people to visit www.firstpeoplesvic.org to seek information directly from the Assembly.