CANBERRA -- Just when it seemed the Turnbull Government was there in its bid to pass its school funding package, a retiring Liberal senator is threatening to abstain or cross the floor to protect the Catholic schools sector.
The twist adds a degree of difficulty to Education Minister Simon Birmingham's job in getting the multi-billion dollar Gonski 2.0 package over the line before parliament rises on Thursday for a six-week winter break.
— Sky News Australia (@SkyNewsAust) June 18, 2017
"My legacy very strongly is to support Catholic schools," Back has told the ABC's AM program.
"Unfortunately, until I am convinced that the proposals in place will not disadvantage Catholic schools, and independent schools for that matter, then I have indicated to the Minister, 'Please don't make me vote against the government in my last week in the Senate'."
The loss of Back, a former member of the Catholic Education Commission who ends his senate term this week, would leave the Government needing 11 votes.
Back says he's indicated to the govt "please don't make me vote against the govt in my last week" #auspol
— Uma Patel (@umabp) June 18, 2017
Under the current Gonski 2.0 deal being negotiated, there's an additional $18.6 billion going into schools generally, but the rate of increase is quicker for public schools than the Catholic school system.
The Catholic sector is expecting schools will close, but the Government argues it is redistributing funding based on need.
Debate is set down for Wednesday and Birmingham was already balancing off the Greens and the rest of the crossbench in the need for 10 votes, with reports of a compromise of an extra $5 billion over ten years for schools to get the Greens over the line. This compromise is also being reported as an extra $1.5 billion over four years.
Some of the Greens' concerns have been met and the party is expected to decide on its position over the next few days. Meanwhile Pauline Hanson's One Nation party reportedly will vote for the schools funding package.
The Minister will neither confirm nor deny any new deal, but insists the Catholic sector will be better off under any revamped Gonski package.
"If you had all of the mythical Labor Party money thrown at different arrangements, if you left in place all of the different special deals, well there might some giant advantage that exists for one particular sector," Birmingham told RN Breakfast.
"The truth is the funding is going up and it is going up from $6.3 billion this year to $9.7 billion by 2027.
"$3.4 billion extra for Catholic education around Australia; 3.5 percent growth per student per annum on average over the decade."
He's describing Senator Back's concerns as "small technical issues" that can be resolved.
"I am confident that we will have support within the Government ranks to deliver the needs-based funding that Australians schools deserve," Birmingham said.
"Chris is a good man and I am absolutely certain that he wants what is best for all Australian students."
Senator Back's preference is to delay the vote for 12 months and hold another review of the current system.
Click below to follow HuffPost Australia Politics on Facebook!
ALSO ON HUFFPOST AUSTRALIA