The federal government on Friday released a 40-page report of an investigation into former chief executive Christine Holgate's decision to give the watches to four staff in November 2018 as a reward for clinching a banking deal.

Australia Post chair Lucio Di Bartolomeo told an inquiry in November he would have blocked the purchase of the luxury watches if he was in charge when the gifts were doled out to senior executives.

The investigation found the board "did not consider or approve the purchase of the Cartier watches".

"There is no documentary evidence that the board approved the expenditure for, and none of the board members interviewed recalled any discussion about the purchase of, the Cartier watches.

"There is contradictory evidence as to whether the former group CEO and managing director informed the former chair that it was her intention to purchase the Cartier watches or whether the former chair approved the commitment of funds for this purchase.

"No definitive finding can be made in this regard."

However on the positive side for the now-resigned Ms Holgate, the investigation found "no indication of dishonesty, fraud, corruption or intentional misuse of Australia Post funds by any individual involved in the matters relating to the purchase and gifting of the Cartier watches".

But the purchase was found to be inconsistent with public service obligations imposed on the board governing the "proper use and management of public resources".

Australia Post has since launched a review of policies in relation to gifts and benefits.

The investigation also found - based on a preliminary review of a limited set of credit card usage records - it appeared there were "potentially other instances of credit card usage for charges that, although for lesser amounts than the expenditure on the Cartier watches, may also be inconsistent with public expectations and Australia Post's policies".

Law firm Maddocks was engaged by the finance department to support the investigation.

Ms Holgate has previously stated she did nothing wrong other than fail the "pub test" for some people.

She argued the executives given the watches had done an "inordinate amount of work" to negotiate a financial services deal with three banks.

Prime Minister Scott Morrison said at the time it was revealed he was appalled and shocked by the behaviour.

Australian Associated Press