A contentious highway upgrade has again come under scrutiny after revelations a land deal was struck between Victoria's roads department and the former Aboriginal cultural heritage authority which approved the development.

Key points: Documents show the Aboriginal authority that signed off on the Western Highway plans benefited from the project

Documents show the Aboriginal authority that signed off on the Western Highway plans benefited from the project The roads authority defended the land deal as entirely legitimate

The roads authority defended the land deal as entirely legitimate The head of the Victorian Aboriginal Heritage Council has called for an audit of the approvals process

It is one of the country's busiest rural highways, and fast becoming the most contentious.

The fate of sacred trees on a site planned for Victoria's Western Highway extension, near Ararat, has brought protesters from around the country and attracted international attention.

Aunty Sandra Onus, the Djab Wurrung elder who helped set up a makeshift tent embassy at the site said the protesters had no plans to move on, despite police warnings.

"They've had 200 years of taking our land, of doing what they like," Ms Onus said.

"And this last little bit here — it's only a 12 kilometre stretch of road — give us a break."

Ms Onus and her supporters say the land is sacred and that generations of women have given birth in its hollowed-out trees.

Now, she has accused the Victorian Government of "dangling carrots" in its effort to push the road through the approvals process.

Protesters have been gathering at the Djab Wurrung Embassy to prevent the destruction of the site. ( ABC Ballarat: Dominic Cansdale )

Documents reveal million-dollar deal

Documents uncovered by the ABC show the Aboriginal authority that signed off on the highway benefited from the project.

VicRoads signed the lucrative land deal with the now-defunct Martang Registered Aboriginal Party, which formally approved the highway project in 2013.

Twelve months later, in October 2014, Victoria's roads department gave the authority — all members of one family — hundreds of hectares of land east of the highway, as part of a Trust for Nature covenant.

Martang's business arm bought the land and was then refunded the cost through the covenant.

In return for conserving the site from development, Martang was promised annual royalties amounting to hundreds of thousands of dollars over ten years.

It was part of a requirement to offset the road's destruction of native vegetation, that the department was obligated to meet before works could start.

The Elmhurst property that was given to Martang through a Trust for Nature covenant in 2014. ( ABC Ballarat: Dominic Cansdale )

In total, the agreement cost taxpayers more than $1 million.

In a statement to the ABC, a spokeswoman for VicRoads said the land deal was entirely legitimate.

"In line with longstanding practice and the relevant legislation, VicRoads made this purchase as part of a social procurement initiative to support the Registered Aboriginal Party's business and environmental priorities," the statement said.

Martang did not respond to repeated requests for comment.

An attempt 'to attack, insult and undermine'

The Victorian Government said it had already consulted with traditional owners and amended the route's design to protect more than a dozen trees.

Speaking at a press conference last month, Victoria's Transport Minister, Jacinta Allan, said the highway upgrade had been through the necessary legal process.

"It's been through approvals of two environment ministers, it's received approvals from Aboriginal Victoria so we have to now look at how we get on and commence the start of this project," Ms Allan said.

A spokeswoman for Ms Allan said any questions around the agreement were "simply another attempt by the protest group to attack, insult and undermine the authority of both Martang and Eastern Maar — the two [groups] that represent the Djab Wurrung people".

Martang is no longer a recognised cultural heritage authority and was deregistered last month, after legislative changes meant that it no longer met the requirements for registration.

The company and its assets still exist and it continues to receive royalties through the Elmhurst covenant.

Eastern Maar has applied to take its place as the Registered Aboriginal Party for the area in question and its leadership broadly backs the road project.

The corporation's chief executive, Jason Mifsud, offered a statement but did not want to comment specifically on the land deal.

"Eastern Maar's governance arrangements are one of inclusivity," Mr Mifsud said.

"We don't enter into commentary about the way other Aboriginal corporations run their business."

A section of the Western Highway near Ararat. The road connects Melbourne and Adelaide. ( ABC Ballarat: Dominic Cansdale )

Ms Onus said the process needed to be revisited.

"Obviously they think we're all stupid.

"Put it on hold and let's get to the bottom of this. Obviously if it was a flawed process, something has to change."

Calls for audit to restore public trust in deal

Martang alone signed off on the Cultural Heritage Management Plan that allowed the highway to go ahead.

The legally binding document has not been seen publicly and still stands as the legislative authority for the Government to build the highway.

The head of the Victorian Aboriginal Heritage Council, Rodney Carter, said now Martang has been deregistered as a cultural heritage authority, it would be up to Aboriginal Victoria to decide whether to make the document public.

The Government has previously stated that the management plan contained no evidence of significant cultural heritage at the site.

Rodney Carter wants the approvals process to be looked into. ( ABC News )

Mr Carter has called for an audit into the approval process to guarantee future efforts to protect cultural heritage.

"What the audit does allow is another form of diligence around process, for people to perhaps have a defensible position on the plan that's been created," Mr Carter said.

"Was the plan created to its minimum standards?"

Ms Onus said the Government was showing disregard for Aboriginal people.

"They want to put us into the prehistoric book, as if we existed a thousand years ago — that we don't exist today," she said.

"We have a voice and our children have voices, and our grandchildren and so on and so on have voices.

"That's what we're protecting, and we're trying to show, to show you there's a better way, to show you you can walk hand in hand with us, so we can teach one another.

"But until then it will always be a nation of thieves."