Former treasurer Wayne Swan says the lack of governance around the $5 billion Northern Australian Infrastructure Facility is a fiscal risk to taxpayers and has asked the Auditor-General to investigate.

Mr Swan has written to Auditor-General Grant Hehir asking for his office to investigate the potential risks in the fund, saying the investment mandate for the NAIF "provides no real security for the $5 billion appropriated to the NAIF".

"The minister is the sole approving authority and operates in complete secrecy," Mr Swan says.

Former Treasurer Wayne Swan has attacked the lack of governance of the Northern Australian Infrastructure Facility. Rob Homer

"As it is currently structured I believe the NAIF presents the opportunity for a domineering minister to misallocate billions of dollars of public money - without any proper checks or balances."

Mr Swan says there are "more checks and balances regarding a relatively minor grant of $100,000 from the Commonwealth to a community group than there is for a $1 billion provision of finance from the NAIF".