Mr Porter told ABC radio that the government's model for the commission, which would be limited to only investigating criminal matters, was "completely orthodox and followed in many other jurisdictions".

"All corruption and crime commissions have to investigate criminal offences. That is what they do," he said.

But Attorney-General's Department deputy secretary Sarah Chidgey told a Senate estimates committee hearing that state and territory integrity commissions are not only limited to investigating criminal offences.

"They can investigate criminal matters, but also at least a number of them can investigate matters that aren't criminal offences," Ms Chidgey said.

The embarrassing correction came as the minister sought to push back against critics of the government's CIC model, which has been condemned as toothless because of tight limits on its ability to investigate corruption.

The issue has come into sharper focus following the release of an Auditor-General report showing significant political interference in selecting recipients for a $100 million sports grants program.

Mr Porter admitted the proposed CIC would not have been able to investigate the program because there was no suggestion of criminal conduct in its operation.

"There hasn't been any suggestion whatsoever that there has been a criminal offence committed or reasonably suspected by anyone with respect to the [Community Sport Infrastructure Grants program]," the Attorney-General said. "Neither the police nor integrity commissions investigate things that aren't offences. That is just how it works."

Monash University senior law lecturer Yee-Fui Ng said the Commonwealth's CIC model was much narrower than the anti-corruption commissions operating in the states and territories, and which were much more likely to investigate conduct of the kind uncovered by the Auditor-General in his report.

"The Commonwealth model is a lot weaker than we see in the states because they can investigate accusations of corruption, and that is a lower bar than just investigating criminality," Ms Ng said.

The law lecturer said New South Wales' Independent Commission Against Corruption is able to initiate investigations and hold public hearings into allegations of corruption, including involving ministers, ministerial staff and public servants.

She said this was "a more robust model" than the one proposed by the federal government.

The government is yet to present its legislation to establish the CIC but has indicated it will be an independent statutory body with two branches - one covering law enforcement and the second the public sector - empowered to investigate allegations of criminal corruption.

It had undertaken to release a draft bill by the end of 2019, but late last year Mr Porter said the government was still conducting consultations and would unveil its proposal early this year.

Ms Chigdey confirmed that the Attorney-General had been provided with "multiple versions" of an exposure draft of the bill, and it was up to him when he chose to release it.

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Pressure on the government to establish the federal integrity commission has ratcheted up since the Auditor-General's sports grants report which showed the office of the-then Sport Minister Bridget McKenzie intervened in the process to direct grants toward marginal and targeted electorates in the lead-up to the last election.

Since the report's release it has been revealed 136 emails about the grants program were exchanged between the Sport Minister's office and the Prime Minister's office, including several in the hours after the election was called in April last year.

Mr Porter admitted the proposed CIC would not investigate matters like the sports rort case, but insisted it would have the power to inquire into a "very wide range of Commonwealth offences which pertain to issues of integrity, which went to issues of corruption".

"There are offences on the Commonwealth books such as abuse of public office, which is a very broad ranging offence," but added that there was no suggestion such a breach had occurred in the sports grants program.

The Attorney-General emphasised that in the first instance, investigations would be undertaken by the Auditor-General, who would then make recommendations to the CIC about matters to pursue.

But Ms Ng said the government's proposal falls short of what is needed.

She said the requirement that there be reasonable suspicion of corruption amounting to a criminal offence before the CIC could begin investigations was too onerous, and was a much higher bar than facing state ICACs, who have exposed criminal corruption through investigations based on allegations.