British engineering giant Rolls-Royce has paid $1.1 billion to settle corruption probes in the UK and US and admitted to using oil industry fixer Unaoil to pay huge bribes in several countries.

Statements released overnight by the US Department of Justice and the UK Serious Fraud Office reveal that information uncovered by Fairfax Media's 2016 expose of the Unaoil bribery scandal has been used to make serious corruption findings against Rolls-Royce.

Rolls-Royce is one of several major multinationals that used Unaoil to win contracts in oil and gas producing nations via a system that involved Unaoil bribing government officials responsible for awarding the contracts.

The settlement highlights the relative weakness of Australia's anti-bribery system in which federal police investigators have amassed significant information about Australian firm Leighton Holdings' corrupt use of Unaoil to win huge deals in Iraq, but have struggled to charge the company or any individual.