About half of the spending was by the government's 21 departments, and the rest was spent by universities, TAFE and other public sector entities.

The Newman government's Strong Choices campaign was the biggest advertising spend over the three years, at $7.6 million in 2013-14 and $3.7 million in 2014-15.

The spending was examined in a Queensland Audit Office report into government advertising.

It includes the cost of placing ads but does not include the cost of planning, creating or evaluating campaigns.

Strong Choices cost the state more than $70 million in advertising, scoping studies and consultation and was blamed for contributing to the Newman government's loss at the 2015 election.

The top five most expensive advertising campaigns under the last year of the LNP government, and the first five months of the Labor government in 2014-15, were: Strong Choices; Health Guarantee; Obesity, Delivering Outcomes; and My Smoking phase 3.

The top five campaigns in 2014-15 totalled more than $12 million.

The top five most expensive advertising campaigns under the first year of the Palaszczuk Labor government in 2015-16 were: If it's flooded, forget it; Childhood Immunisation; Drink Driving; Straight Answers; and Quit Smoking.

The top five campaigns in 2015-16 totalled $8.9 million.

The Audit Office made six recommendations, including that departments prepare formal reports after campaigns which summarise results, cost-effectiveness and insights to inform future campaigns.

It said there were legitimate reasons for governments to advertise, such as raising awareness, educating the public and generating behavioural change.

But taxpayer funds must be used to provide information to the public, not gain political advantage.

One of the campaigns under the microscope was Treasury's Queensland First Home Owners' Grant advertising campaign.

Departments are required to submit major campaigns to the Government Advertising and Communication Committee for approval and minor campaigns go to the Department of Premier and Cabinet for noting.

When Queensland Treasury first submitted its campaign to the committee in May 2016, it did not receive approval to proceed.

The committee supported the campaign in principle, however it questioned the amount of spending, noting it would be one of the highest-spending campaigns for the 2015-16 financial year.

The committee approval process states that campaigns must not be split into segments to avoid being classified as major and therefore subject to the committee's approval.

Treasury split the campaign into segments, with an early First Home Owners' Grant campaign running on paid radio and online while continuing to plan, develop and implement another campaign, including TV ads.

By splitting the campaign into two, it was able to get its First Home Owners' Grant campaign into the market quickly.

But as a result, it advertised before receiving committee approval.

The early campaign cost $137,708.

There are no repercussions for departments when they do not comply with the committee approval process or its code of conduct.

Treasury also released creative material on its Facebook and Twitter accounts while the committee approval process continued, but the code was not clear that departments should not do this.

The Audit Office questioned the campaign itself, and said Treasury had not justified the need to use advertising to educate the public about the grant, when it was finally approved.

"Queensland Treasury's campaign was approved by the committee despite the fact that it did not effectively justify the need to use advertising as the communication medium," the Audit Office report said.

"This means neither it nor the committee can be sure that the most cost-effective way of educating the public was selected."

A Queensland Treasury spokesman said as part of the announcement the grant would be boosted to $20,000 in 2016, the government approved advertising so its benefit to the community could be maximised.

He said the community gave in-principle support to the promotion before the budget and approved the full package in January 2017.

"In the interim period between announcement of the enhanced QFHOG and the final approval ... for the complete campaign, Treasury engaged in a series of low-cost and low-intensity media placements focused on digital and radio media," the spokesman said.

He said there was now TV, cinema, radio, print and digital advertising worth $1.4 million aimed at reaching first home buyers and approved by the committee.

Since it was announced, 4125 grants worth $82.5 million have been approved.

The number of monthly grant applications rose from 123 in July 2016 to 728 in March 2017.