Griffith University professor AJ Brown made the comments at a Senate Select Committee investigating the adequacy of the federal government's current framework to address corruption and misconduct and whether a national integrity commission should be created.

"I think the committee and the Parliament should be working on the basis that the prevalence of low-level petty corruption and potentially systemic mid-level corruption on a Commonwealth level is probably higher than anybody has currently documented," he said.

"We know that because every time someone does lift a rock and have a look, we find more than people claimed prior to the rock being lifted was there."

Professor Brown said there was a high corruption risk in almost every area of significant Commonwealth investment, whether it was regulatory or service delivery.

"The Commonwealth is responsible for the lion's share of the nation's money and there's only so much that fraud control and financial control mechanisms can do to monitor corruption risks," he said.

Speaking about Queensland, Professor Brown said the the anti-corruption aspects of the Crime and Corruption Commission began to be "whittled down" during the former Newman government, which prioritised its organised crime function.

"Both in terms of political mandate, legislative authority, legislative obligations, resources, giving it extra money, but only for the organised crime functions, not for the anti-corruption functions," Professor Brown said.

"What happened during that period was a skewing of the commission through fairly explicit government policy."

Professor Brown said, over time, the CCC appeared to have managed the conflict between its obligations well.

CCC chief executive Forbes Smith was critical of a Newman government change to require complaints to be lodged with a statutory declaration.

Mr Smith said it resulted in a "marked fall" in complaints to the CCC as it required significantly greater effort to make a complaint.

"The current government rescinded that requirement and I think it's probably no coincidence that our complaints have started to increase again," he said.

But Mr Smith was no fan of the statutory declarations, despite decreasing the workload.

"I'm very strongly against that," he said.

"I think it's important to realise that we're a commission for all, in our case, all Queensland and not everybody has the capacity or ability to make a statutory declaration.

"They should be able to either write a letter or ring us ... You should be making a complaint as easy as possible.

"If that leads to frivolous complaints being made, well we'll just deal with that in the course of business."

Mr Smith said even if information did not lead to an investigation, it helped to build an intelligence profile on people or systems.

In December, the CCC recommended that a new offence be created making it illegal to publicise allegations of corrupt conduct against a candidate in the lead up to local government elections.

It came after the CCC investigated whether an offence should be created to stymie "vexatious" complaints.

Mr Smith told the select committee there was a spike in complaints during local government election campaign.

"It seemed obvious to us, at least, that they were designed to do some collateral damage to candidates and opponents," he said.

"A very clear example was somebody put in a complaint on Friday, the day before the election, and withdrew it on the Monday.

"It seemed to us that if a person is genuinely interested in having an allegation of official corruption or corrupt conduct investigated, that there is no real need to publish that fact."

Mr Smith also said recent public hearings into the 2016 local government elections generated more complaints "and they also helped generate discussion about how the problems that were identified through the hearing process could be resolved".