An internal review of accounts at Rupert Murdoch's Australian operations prompted by the British hacking scandal found "no evidence" of phone tapping or untoward payments, the company said Monday.
But News Limited also announced strict new editorial guidelines only allowing the use of private investigators in "exceptional circumstances" and with the express permission of senior staff.
The Australian firm conducted a three-month review of major payments dating back to 2006 after the firestorm over phone hacking at its British counterpart News International which saw the best-selling Sunday tabloid News of the World axed.
Almost 700,000 transactions worth Aus$335 million (US$345 million) were scrutinised by a team of 26 auditors and the company said it had found "no evidence of illegitimate telephone surveillance or payments to public officials".
News Limited said private investigators had been used on a "small number of cases" and, "where required", the firms had been asked to retrospectively provide written assurances that their work processes were legal and legitimate.
The cases of two people who came forward in Australia after the British scandal and claimed their phones had been hacked had also been examined and News Limited said "no evidence was found to support the claims."
Reporters responsible for the stories in question were extensively interviewed and were found to have "applied normal practices of professional journalism," it added.
But the company said it would roll out a new overarching editorial code of conduct in response to the British crisis, which saw two of Murdoch's top executives quit and the media magnate himself hauled before parliament.
The code would include strict new provisions on only using private investigators under "exceptional circumstances" and for work that "checks, verifies or establishes facts" for the sake of accuracy.
All investigators would have to be cleared by an editor, divisional head and group editorial director and would have to provide written assurances that they would not engage in illegitimate surveillance, News Limited said.
Two retired judges reviewed the audit and approved its conduct and subsequent measures taken, though they did stress that their opinion was based on "reports given to us" rather than observation of the process.
Australian-born Murdoch controls 70 percent of newspapers in his home country, has a stake in broadcasters Sky News and Fox Sports, and is angling to run the Australia Network, the international public TV channel.