The Queensland government is considering temporarily funding a $100 million road upgrade for the Adani coal mine, despite the premier's promise no taxpayer funds will go to the project.

The ABC says documents obtained under right to information show the main roads department has been investigating funding options for the upgrade for almost 18 months, with any taxpayer funds used to be recovered from Adani later.

No decision has yet been made, but the opposition has accused Premier Annastacia Palaszczuk of breaking her election promise not to spend taxpayers’ money on the mine or associated infrastructure.

By Tracey Ferrier