A Greens MP has described the Turnbull government's school funding plan as a "bastardisation", casting doubt over whether the minor party will support Gonski 2.0.
The Greens have yet to rule out support for the plan, as it awaits the outcome of a Senate inquiry into the legislation.
But Adam Bandt said he would be voting against it, insisting he would not support funding cuts to disadvantaged students.
Gonski's original vision had been "bastardised", he told parliament on Wednesday.
"It's been bastardised by Labor and now again by the coalition," the Greens MP said.
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"The Greens want to see the original Gonski vision realised and that's why we'll be fighting for a better deal."
The Greens would use the Senate inquiry to shine a spotlight on the bill and consult parents, teachers and unions to determine what was needed to implement Gonski's original plan for needs-based funding, Mr Bandt said.
The MP said he'd received information that the number of over-funded private schools would grow from 17 per cent to 65 per cent under the government's plan.
Labor has vowed to oppose the plan meaning the government will need to win over 10 of the 12 Senate crossbenchers if it can't get the Greens on board.
