The infrastructure department's "Building our Future" campaign was designed to promote the government's more than $100 billion investment in infrastructure projects around Australia.

The advertising campaign cost $32.1 million and ran between 2018 and 2021 to increase the community's knowledge of urban and regional infrastructure projects being delivered.

Projects included an upgrade of the Brisbane Metro, an extra light rail stop in the ACT and the Nowra bridge.

But an audit report into government advertising released on Thursday found while the department's campaign was free of political content, material was not always presented in an objective and fair manner.

The audit found the department inaccurately reflected federal and state government involvement in some projects.

The department also did not negotiate lower prices for public relations services and paid for some services which were either not delivered, or delivered too late to be used.

The audit office said the department needs to improve its compliance with set campaign guidelines.

It must also make better assessments about whether continuing a campaign is a proper use of taxpayer resources.

The department agreed to implement all four recommendations from the audit office.

Australian Associated Press