Adani is close to locking in the finance for a rail line to service its $16.5 billion Queensland coal mine, the son of the company's owner says.

Karan Adani, who is the CEO of the Indian group's ports business, made the revelation during a video interview with The Economic Times of India.

"We have completed the financing of the mine, the port is already operational. Now we are just closing on the financing on the rail part," he said on Tuesday.

"So once that is done we will start."

Mr Adani stressed the company had all of the necessary government and environmental approvals related to the Carmichael coal mine in the Galilee Basin in central Queensland.

The rail financing for the project was "almost $US1 billion", he said.

The rail line is needed to move coal from the mine to Abbot Point port, which is being expanded.

There had been questions over the rail financing after Queensland Premier Annastacia Palaszczuk last year vetoed a $1 billion federal government loan to Adani for the project.

Previously, Australia's big four banks refused to put up money for the mine, forcing the company to look for funding overseas.

Federal Labor's environment spokesman Mark Butler, who opposes the mine, was sceptical of claims Adani would soon have the $1 billion required for the rail line.

"If I had a dollar for every front page where Adani said it had finance for this new coal mine I'd be a very rich man. Frankly, I'll believe it when I see it," he told Sky News on Wednesday.

"My view about this project has been clear for some time. I don't think it stacks up. I don't think it is in the national interest."

The state Labor government has imposed more than 240 conditions on the Carmichael coal mine project, 132 of which relate to water conditions.

A month ago, the government also insisted Adani find the source of local groundwater before it signs off on the water management plan for the mine.

The Australian Conservation Foundation said the Carmichael mine would damage the Great Barrier Reef, threaten wildlife and the groundwater supply, and "turbo charge" climate change.

"This is not a project that represents the best interests of the community and the natural world we rely on," foundation chief Kelly O'Shanassy said in his statement.

"Now, more than ever, we need a commitment from all political parties that they will stop this polluting coal mine before it wrecks our safe climate and natural world."