One of Australia's most foremost constitutional law experts has also said Mr Morrison's office might have acted unlawfully by interfering in the scheme.

Former sport minister Bridget McKenzie resigned as deputy leader of the Nationals after Prime Minister and Cabinet secretary Phil Gaetjens found she had breached ministerial standards over the $100 million sporting grants affair.

Mr Morrison had previously insisted his office played no role in assessing sporting grants and merely passed on representations.

The Australian National Audit Office told a parliamentary inquiry last week Mr Morrison's office exchanged "comfortably dozens of emails" with Senator McKenzie's office about the grants scheme, and shared a spreadsheet that colour-coded applications based on electorate.

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Through a question on notice, the audit office said on Wednesday there had been 136 emails between key staff members in Mr Morrison and Senator McKenzie's offices in the six months leading up to the caretaker period on April 11.

Multiple versions of the spreadsheet had been circulated within Senator McKenzie's office, and one version that included $10 million of grants had been shared with the Prime Minister's office.

Labor leader Anthony Albanese accuses Mr Morrison of misleading the parliament over his staff's role in the affair. He denies this.

Meanwhile, constitutional law expert Anne Twomey says the Prime Minister's office did not have the power to dictate where grants were allocated.

In a submission to the inquiry, Professor Twomey said there were lingering questions over whether Senator McKenzie had the legal authority to approve grants.

"The power to make the grants for particular purposes was conferred by statute upon the Australian Sports Commission and the public money was appropriated to it for these purposes," Professor Twomey wrote.

"The minister had no power to approve the grants and her action in this regard was unlawful. Any action in pressuring the Australian Sports Commission to nominate the minister as the approver of the grants and confer additional discretion upon her breached the Statement of Ministerial Standards."

This absence of power extended to the Prime Minister's office, Professor Twomey wrote.

"Just as the minister had no lawful power to approve the grants, the offices of the Prime Minister and Deputy Prime Minister had no power to direct how the decisions were to be made," she said.

Professor Twomey also said it was "grossly unfair" that 272 projects had commenced works and eight had already finished in breach of the program's guidelines.

Given the failure to make the decisions in an impartial and procedurally fair manner, the legality of the decisions could be challenged on several grounds, Professor Twomey said.

"Large amounts of public money were spent unlawfully," she said.