Federal Labor is piling pressure on Bridget McKenzie to step down, accusing her of neglecting her duties while the so-called $100 million sports rorts scandal rolls on.
The fate of the deputy Nationals leader and agriculture minister could come to a head this weekend, as newspaper reports unearthed further revelations.
Prime Minister Scott Morrison has asked his head of department Philip Gaetjens to investigate whether any part of Senator McKenzie's handling of the $100 million Community Sport Infrastructure Program breached ministerial standards.
Mr Morrison is expected to hear back as soon as Sunday.
An auditor-general report found the program favoured coalition marginal and targeted seats before last year's federal election.
The audit found in the third round of the program, 73 per cent of projects given funding were not recommended by Sport Australia.
Labor's agriculture spokesman Joel Fitzgibbon said Australia's farmers are effectively without a minister because Senator McKenzie remains engulfed in a controversy of her own making.
"The prime minister must replace Bridget McKenzie," Mr Fitzgibbon said in a statement on Saturday.
"The agriculture sector has endured a terrible drought and now a shocking bushfire season that isn't over yet. The damage to the agricultural sector is massive and flow-on effects in regional towns will be significant."
The Weekend Australian reports two of Mr Morrison's senior staffers were involved in handling funding applications under the grants program before presenting them to Senator McKenzie when she was sports minister prior to the last year's federal election.
Mr Morrison has rejected suggestions that funding allocations originated from his office.
Nine newspapers also reported that Senator McKenzie signed off on more that $1 million in grants for shooting clubs and associations, potentially opening her up to further allegations of conflicts of interest.
Senator McKenzie, a keen shooter herself, has repeatedly refused to step down from her leadership role in the Nationals party and from the government front bench as agriculture minister.
Mr Gaetjens was given the additional task of looking at whether Senator McKenzie breached rules in regard to her non-declaration of the membership of a Victorian gun club which received $36,000 from the program.
The minister has argued she did not need to declare the membership as it was a gift provided to her in January 2019 and round two funding from the program became available in December 2018.
And, as the gift was valued at less than $300, it did not meet the threshold for declaration, she said.
Nationals Leader and deputy prime minister Michael McCormack has defended his deputy and called out his colleagues for speaking anonymously to the media and positioning themselves to replace Senator McKenzie.
If the minister is sacked, it is likely to trigger instability in the coalition government.
Australian Associated Press