Labor senator Kimberley Kitching has defended calling a $250 million aircraft currently under order by the Royal Australian Air Force as Malcolm Turnbull's "private jet".
The senator questioned air force officials over the plane in Senate Estimates this week.
Her questioning revealed the second-hand Airbus A330 cost $60 million and would be fitted with a $188 million upgrade, which would make the tanker suitable for carrying high-value VIPs like the prime minister or the governor general.
The upgrades would include an improved communications suite and the "cabin modification", officials said.
Senator Kitching later wrote on Twitter the government was spending $250 million on the "PM's new private jet".
The comments drew strong criticism from government ranks.
Nationals MP and new Veterans Affairs minister Darren Chester said it was "stupid" and pointed out the jet would be used by prime ministers from "both sides to do their jobs safely" over the coming years.
Defence Industry Minister Christopher Pyne said the comments reflected poorly on Bill Shorten.
"Shorten caught by an exploding cigar, having being briefed and agreed on the need for a new RAAF plane, now attacking it. I presume he and Senator Kitching will rule out using it if he ever manages to become PM?" Mr Pyne wrote on social media.
Senator Kitching's used Senate Estimates to query the details of the modifications to the plane.
"Will they have an inbuilt entertainment system?" she asked in a hearing on Wednesday.
The senator also asked about on-board wifi and private bathrooms, and criticised the plane's limited capacity, which will be about 80 seats.
Senator Kitching defended the comments on Sunday, posting again on Twitter.
"Only in Canberra could asking reasonable questions about PM Turnbull spending $250M on PM's plane be deemed outrageous," she wrote.
