Australia's top universities are shaking their heads at the federal government's proposed reforms, saying they will lead to lower quality education.
Group of Eight chair Margaret Gardner says the changes need significant amendments.
"We would have preferred a longer and more consultative process on what we believe can and should be significant reform to higher education," she told a Senate inquiry on Tuesday.
"However, we believe that amendments to this bill - significant amendments - can make a workable bill, and a workable bill should and can be produced."
The government says the changes will make an extra 100,000 university places available.
But Professor Gardner argues the plan results in less funding per student so will hurt the quality of education.
The proposal more than doubles the cost of some humanities courses in a bid to encourage people to enrol in courses the government argues lead to higher employability.
Science and maths would be among the degrees made cheaper, along with psychology, agriculture, environmental sciences and health.
"There is no reason that students should pay such widely divergent proportions of cost of their degree," Prof Gardner said.
"We need to ensure this package is improved through amendment and is internally coherent, and delivers for the overall objectives for a sustainable, quality and equitable higher education system."
Science & Technology Australia says the current bill cuts funding for STEM places, having the opposite impact of the government's intention.
"We urge the Senate to ask the government to avert the proposed cuts in the legislation to STEM as a condition of Senate support to pass the bill."
Universities have not been given the modelling the federal government is using to justify its changes.
Australian Technology Network of Universities executive director Luke Sheehy said the government was using 2019 data which wasn't publicly available.
ATN doesn't support the bill in its current form.
Mr Sheehy says six changes are needed, including getting rid of the proposal to remove access to government-subsidised places for students who fail half of their first eight subjects in a degree.
ATN also wants improved undergraduate access for all Indigenous Australians, not just those in regional areas.
University of Sydney's vice-chancellor Michael Spence wants the government to revise and resubmit the changes.
"Think about what you're trying to achieve here and how you might achieve it in ways that don't have perverse incentives in the education space and don't do damage to Australia's research effort."
The National Union of Students described it as a significant attack on the sector, calling the bill to be withdrawn.
Education Minister Dan Tehan is negotiating with the Senate crossbench in a bid to pass the bill, after a recent vote revealed the government didn't have majority support.
Labor's education spokeswoman Tanya Plibersek says the changes will make it harder for year 12 students to go to university.