Nationals leader Michael McCormack is under pressure again after suffering another damaging internal leak.
Mr McCormack's office encouraged Nationals to charge taxpayers for flights and accommodation to a lavish party in Melbourne.
A partyroom meeting had been timed to coincide with the centenary celebrations next month, according to a text message leaked to The Courier-Mail.
Mr McCormack has sought advice from the Independent Parliamentary Expenses Authority to ensure the plans are above board.
Politicians can bill taxpayers for travel expenses if trips are for the "dominant purpose" of conducting parliamentary business and represent value for money.
Attending a formal party meeting falls within this scope.
"IPEA advises travel to this event would, in broad terms, meet the above definition," a spokeswoman for Mr McCormack told AAP on Wednesday.
"But as always, this is a matter for MPs and senators to determine."
Nationals frontbencher Mark Coulton concedes the use of taxpayer funds does not pass the "pub test".
"Not on the surface," Mr Coulton told the ABC.
"But quite often there's more, you know, I more likely will be in Victoria for the week, there's other ministerial responsibilities to be down there."
Mr Coulton is frustrated by the latest episode of Nationals infighting.
"I didn't go into politics to be part of a soap opera," he said.
"The people that I represent in regional Australia couldn't give a rat's toenail, quite frankly, about the machinations of the National Party."
Nationals senator Matt Canavan, who quit cabinet to vote against Mr McCormack in leadership spill last week, downplayed the expense claim controversy.
Senator Canavan pointed out the trip had not yet taken place.
"Of course what I'll do is make sure all expenditure of taxpayers' dollars is done appropriately," he told reporters.
"This is an event in the future, it hasn't happened, and my understanding is Michael, his office and the National Party are getting advice on this issue, which is the right thing to do."
The travel advice to Nationals came from the deputy prime minister's chief of staff.
"The intention was to hold a party room meeting but this was subject to IPEA advice and confirmation closer to the time," Mr McCormack's spokeswoman said.
"The location of this meeting is a matter for the National Party and a decision will be made at the regular party room meeting in Canberra on February 24."
The leaked text message was clearly designed to damage Mr McCormack.
A small group of Nationals still want him gone as party leader.
Queenslander Llew O'Brien quit the party after the failed coup, claiming his defection was partly motivated by the Nationals' use of taxpayer funds for travel costs.
Mr O'Brien pointed to one party meeting timed to coincide with the Melbourne Cup.
Hours after he resigned, a handful of Nationals rebels conspired with Labor to hand him a parliamentary promotion, humiliating the government by torpedoing their pick for the job.
Australian Associated Press