Labor Senator Penny Wong made the accusation during Senate estimates hearings on Monday. She pointed out that while the funding approval was dated April 4 2019, Senator McKenzie wrote to Prime Minister Scott Morrison six days later, on April 10, with a list of projects she "intended" to fund. At 8.30am the next day, April 11, the government entered caretaker mode. Fifteen minutes later, Senator McKenzie sent the list of approved projects to Sport Australia.

Labor has quizzed the government and officials over the discrepancy in timing, after the dates were revealed by Auditor-General Grant Hehir in his investigation. Senator Wong suggested at Senate estimates hearings on Monday that it had been deliberately backdated.

But government senator Mathias Cormann, describing the accusation as outrageous, said he had checked with Senator McKenzie, who was "unequivocal to me that she signed the brief on the 4th of April". Any communication with Mr Morrison after that was about the announcements.

Senator Wong asked whether backdating a brief would amount to a criminal offence, to which departmental deputy secretary Stephanie Foster said she genuinely didn't know but would check.

Ms Foster said she hadn't seen the brief that Senator McKenzie sent to Mr Morrison on April 10 had "no visibility or knowledge " of it.

Earlier, acting deputy secretary Cath Patterson said when Labor Leader Anthony Albanese asked Mr Morrison about it in parliament, her staff had searched for records of the brief but had found nothing and believed it had been an email rather than a formal letter.

The government has been under enormous pressure since January when Mr Hehir's audit was released, finding that Senator McKenzie largely ignored the scores that Sport Australia gave to sports projects, and instead approved projects based on whether they were in marginal electorates and electorates being targeted by the government in the election.

Senator McKenzie resigned as sports minister over a conflict of interest, when it was revealed that she hasn't declared her membership of a shooting club that received funding. But questions remain about Senator McKenzie's process for deciding which clubs would get money from the $100 million fund.

The auditor reported that her office had drawn up a colour-coded spreadsheet with columns identifying which party held the electorate and whether the electorate were marginal or targeted by the coalition.

Mr Hehir found grants were skewed towards marginal and targeted electorates, which were more successful than they would have been if funded according to merit. In the first funding round, for example, the 17 "targeted" electorates received 79 grants, instead of the 54 they should have received if decisions had been made according to the merit criteria.

An adviser in Senator McKenzie's office has conceded the office did consider electorate status, but claimed the aim was to ensure a fair spread of projects.

Departmental secretary Phil Gaetjens has disputed Mr Hehir's finding, saying there was no evidence the process in the minister's office was "unduly influenced by reference to 'marginal' or 'targeted' electorates".

Ms Foster told Monday's inquiry that she had found no evidence of bias, with projects tagged as marginal or targeted funded at a rate of 32 per cent, compared with a 36 per cent success rate for projects in other electorates.

After the damning audit report was released, Mr Morrison asked Mr Gaetjens to advise him on Senator McKenzie's handling of the program. Mr Gaetjens' report has not been released.

Separately, the Senate has set up an inquiry into the sports grants. Mr Gaetjens will appear before the inquiry on March 16.

The government has refused to release the spreadsheet, claiming public interest immunity, prompting Senator Janet Rice to ask why government backbencher Eric Abetz, one of the two Liberals on the Senate inquiry, had been given access. Senator Cormann said Senatr Abetz did not have an unredacted version of the spreadsheet.

Ms Foster told Monday's hearing that the spreadsheet attached to the April 4 funding brief included the colour coding by party, but not the column on marginal and targeted electorates.

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