An anti-corruption unit of the Iraqi Oil Ministry reportedly is investigating whether a Leighton Holdings subsidiary paid bribes for information relating to an oil project in Iraq.

The allegations involve $US1.3 billion ($A1.21 billion) of tenders for a project known as the Sea Line Project, the Australian Financial Review says.

Officials within the oil ministry's Inspector Generals office have said they considered it "more than likely" that Leighton Offshore was given advance details of rival bids in order for it to offer the lowest price, the paper reported.

This follows news in February that the Australian Federal Police is investigating whether Leighton Offshore made payments in connection with work to expand offshore loading facilities for Iraq's crude oil exports.

No charges have been filed against Leighton and the company declined to comment on the latest matter, saying that the police investigation was continuing.

"We do not know whether there has been any wrongful or illegal conduct or whether there will be any adverse financial consequences for Leighton," a spokesperson told the Australian Financial Review.