The Palaszczuk Government is still considering covering the estimated $100 million upfront cost of road access for Adani's Queensland mine, despite promising no taxpayer funds would go to the project.

Key points: Labor Government promised not to fund Adani during election campaign

Labor Government promised not to fund Adani during election campaign Documents show possible road funding is still under consideration

Documents show possible road funding is still under consideration Adani says payments will comply with government conditions

The ABC can reveal the State Government is negotiating a state takeover of about 90 kilometres of local dirt roads that must be upgraded if Adani is to gain year-round access to the proposed Carmichael mine site in central Queensland.

Documents obtained under a right to information (RTI) application show the Queensland Government's powerful Cabinet Budget Review Committee made a decision about providing state funding of the upgrade before July last year.

But the documents also showed that almost a year later, the Department of Transport and Main Roads and the Office of the Coordinator-General were still negotiating terms of the upgrade with Adani and Isaac Regional Council.

The files reveal that before last November's state election, the department already had more than 2,200 pages of documents — including 650 pages of drawings and specifications — relating to potential state government funding of the road upgrade.

When the potential deal was reported during the campaign, Queensland Premier Annastacia Palaszczuk stood by Labor's promise the mine would not receive state funding.

Asked if that included associated infrastructure, Ms Palaszczuk said: "I don't think so — we said no taxpayers' money would go towards it."

But Ms Palaszczuk did not rule out helping the council fund the access road.

Ms Palaszczuk said during the election that taxpayer funds would not go towards Adani. ( AAP: Darren England )

Transport and Main Roads Minister Mark Bailey said the same day there were "no public funds going into the Adani project in any shape or form".

His department last month told the RTI applicant, the consultancy Energy and Resource Insights, that some details of possible state funding of the upgrade would be kept secret because "this issue is still subject to significant deliberation and negotiation".

"No firm decisions have been made about the upgrade of the access road," the department said.

Opposition claims Premier 'lied to Queenslanders'

Opposition Leader Deb Frecklington said the State Government's ongoing negotiations showed "Annastacia Palaszczuk has lied to Queenslanders and has broken yet another election promise".

"Palaszczuk said one thing to secure Green preferences but is clearly doing another — Queenslanders are sick of politicians who don't stick to their word," Ms Frecklington said.

Ms Frecklington noted the State Government, with Greens support, blocked an Opposition motion to release details of another "sweetheart" deal with Adani to allow it to defer its royalty payments.

Map showing Carmichael Coal Mine and Rail Project in central Queensland. ( Supplied: Queensland Department of Transport and Main Roads )

Adani previously committed to carrying out the upgrade of Moray-Carmichael Road and the Elgin-Moray Road in order to keep it open in the wet season, a commitment noted in a coordinator-general report in 2014.

But by February 2017, Isaac council was concerned about the cost of maintaining the local roads.

It voted to apply for a state takeover because "the potential financial impact of the roads upgrade is unacceptable to council due to impact on depreciation".

The council said it would transfer part of its interest in a 2016 mining compensation agreement with Adani to the State Government, which would have to reach an infrastructure agreement with the miner to enable it to recover costs.

Weeks earlier, an email from assistant coordinator-general Kerry Smeltzer noted one of the "actions" after a meeting with Main Roads and the council on the road upgrade was to "discuss funding arrangements with QTRIP [Queensland Transport and Roads Investment Program]".

The issue generated documents between March and July 2017 relating to the CBRC, a committee in which the Premier, Treasurer and two senior ministers rule on significant spending that is not covered by existing budgets.

They included documents which "record the official discussions about the implementation of a CBRC decision".

Documents show plans to 'investigate' funding

Sorry, this video has expired Who is Gautam Adani? (Photo: AAP)

Transport department emails from July 2017 stated there was "no funding or planning" to build the road or infrastructure to open up the Galilee Basin.

But four months later, a departmental email notes a meeting between the coordinator-general, the director-general of the Office of the Premier and Cabinet and the Isaac council about making an access road to the proposed Carmichael Mine "state controlled".

A September 19 document titled "Adani Projects — Actions progress table" includes the topic "investigating options for funding/upgrading Carmichael-Moray Rd".

Two days later departmental staff were discussing "Adani road estimates - Further Update".

The Queensland Government was contacted for comment but had not responded by deadline.

However this morning, a Queensland Government spokesman said in a statement: "As stated during the recent election campaign, we are happy to speak with local councils about their infrastructure needs."

"Significant projects can impact on local road networks and improvements to those networks can benefit the greater community," the spokesman said.

"Costs associated with major projects are recovered by the state on a commercial basis."

An Adani spokeswoman said it continued to work with the Main Roads department and council, and all payments would comply with State Government conditions, local government laws and council revenue policies.

"Like many other major projects, Adani Australia has strict project conditions that require it to work with the Department of Transport and Main Roads and regional councils regarding the use and maintenance of publicly-owned roads impacted by our project," the spokeswoman said.

Isaac Mayor Anne Baker told The Australian newspaper last year the upgrade would cost between $60 million and $100 million, which is close to the $1 million per kilometre benchmark for rural roads cited by a Federal Government report.