The Office of the Auditor-General has received two formal complaints about a property deal Christchurch City Council made with a local developer.
The council is spending almost $17 million to buy five properties from developer Dave Henderson.
The deal came after Mr Henderson ran into financial difficulties that include two of his companies facing liquidation proceedings.
The move has drawn criticism from those who believe Mr Henderson contributed to Bob Parker's successful mayoral campaign.
The Office of the Auditor-General says it will decide in the next few days whether to launch a formal investigation.