Senior executives at construction giant Leighton reportedly exchanged emails lamenting a history of misbehaviour in its offshore businesses.
A leaked email reportedly shows two top executives referring to a "disgusting history of incompetence and misbehaviour" and improper "rewards, special bonuses, travel rorts" in its overseas operations, Fairfax Media reports.
Other emails show senior Leighton staff looked at ways to hide a $24 million corrupt payment in Iraq by artificially inflating the costs of providing security, accommodation and other services.
Fairfax also claimed the Australian Federal Police were finalising a brief of evidence against Leighton to present to prosecutors.
Leighton first reported potential corruption in its business to the AFP in 2012.
It has since said it was concerned by the corruption claims but has also accused media of "sensationalising" the allegations.
The scandal has seen at least three former Leighton executives quit their subsequent posts with different construction firms.
Former chief executive Wal King has denied any knowledge of the alleged payments in Iraq.
Leighton shares fell heavily on Monday, but that was partly due to the shares trading ex-dividend, meaning new shareholders are no longer entitled to the company's 57 cents interim dividend.
Leighton shares dropped 90 cents, or 4.1 per cent, to $20.94.
Brokers said the fall also reflected the weaker investor sentiment that pulled the wider market lower.