A potential $1 billion federal government loan to Indian conglomerate Adani for its proposed coal mine has been called into question because comments by the company appear to conflict with infrastructure funding guidelines.

Public finance for Australia's biggest open-cut coal pit has become the latest political battleground, as alarming new footage emerged of the environmental damage done to wetlands bordering Adani's Abbot Point coal terminal in Queensland by cyclone Debbie.

Research by the independent Parliamentary Library, passed to Fairfax Media, found statements by Adani on the financial viability of the Carmichael project in Queensland's Galilee Basin could render it ineligible to accept funding for a mine-to-port rail line from the $5 billion Northern Australia Infrastructure Fund.

In December, Adani spokesman Ron Watson confidently declared that access to the $1 billion concessional loan through the infrastructure fund was "not make or break" for the $16 billion project moving to production. "It's not critical," Mr Watson said of the loan at the time.