The Queensland government has signed a deferred royalties deal with Adani for its $2 billion Carmichael coalmine.

Treasurer Cameron Dick sealed the deal with the Indian-owned firm on Thursday, guaranteeing state revenue amid an opposition election promise to freeze mining royalties for a decade.

“I can assure you that Adani will pay the dollars in royalties they have to pay to the people of Queensland and the taxpayers of Queensland with interest,” Mr Dick said.

“So that’s absolutely locked in now and something we’ve completed as a government.”

The deferred payment agreement is similar to one struck with New Century Resources for their $150 million project near the Burketown and the Northern Territory border.

Royalties Deferral and Repayment Agreements allow miners to delay royalty payments to free up cash flow at the beginning of their projects if they meet the obligation later with interest.

A deferred royalties deal with Adani was rejected by members of the previous Labor cabinet before the 2017 state election.

“I can assure Queenslanders every dollar that is owed to Queensland taxpayers will be paid and it will be paid with interest,” Mr Dick said on Thursday.

The opposition Liberal National Party has promised to freeze mining royalties for a decade if elected on October 31.

Australian Conservation Foundation campaigner Christian Slattery called for the government to release the details of the deal.

He said it was disgrace to allow the mining giant to defer payments.

“The government should immediately disclose the terms of this deal. Queenslanders have a right to know how much revenue and risk has been sacrificed at the altar of Adani’s destructive coalmine,” he said.

The deal is the latest development in a decade-long political and legal battle over the controversial Carmichael project, which has been under construction since July.

Environmental activists and indigenous groups have been fighting against the process and numerous legal proceedings have been lodged against it.

The most recent, brought by activist Ben Pennings in his campaign against the company, was won by Adani.

The Queensland Supreme Court ordered Mr Pennings to remove social media posts encouraging company employees disclose information to him about the project and to stop using confidential information.

The company is building its 10 million tonne-a-year capacity thermal coalmine in the Galilee Basin, which could be expanded to six times that size.

Adani is also building a rail line that will be opened to other companies if it gets the tick of approval to mine the coal-rich region.