The Future Fund must divest the $3 million it has put into a railway for the climate-destroying Adani coal mine, the Greens say.

Greens Economic Justice Spokesperson Senator Nick McKim said.

"This is public money and should be invested for the public good."

"Having already ruled out investing in tobacco products, the Future Fund must urgently get out of fossil fuels."

"This is a bad investment financially, morally and environmentally. To use public funds to cook the planet is an extraordinary error of judgement."